From 632ee200130899252508c478ad0e808222573fbc Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 22 Feb 2010 17:04:45 -0800 Subject: rcu: Introduce lockdep-based checking to RCU read-side primitives Inspection is proving insufficient to catch all RCU misuses, which is understandable given that rcu_dereference() might be protected by any of four different flavors of RCU (RCU, RCU-bh, RCU-sched, and SRCU), and might also/instead be protected by any of a number of locking primitives. It is therefore time to enlist the aid of lockdep. This set of patches is inspired by earlier work by Peter Zijlstra and Thomas Gleixner, and takes the following approach: o Set up separate lockdep classes for RCU, RCU-bh, and RCU-sched. o Set up separate lockdep classes for each instance of SRCU. o Create primitives that check for being in an RCU read-side critical section. These return exact answers if lockdep is fully enabled, but if unsure, report being in an RCU read-side critical section. (We want to avoid false positives!) The primitives are: For RCU: rcu_read_lock_held(void) For RCU-bh: rcu_read_lock_bh_held(void) For RCU-sched: rcu_read_lock_sched_held(void) For SRCU: srcu_read_lock_held(struct srcu_struct *sp) o Add rcu_dereference_check(), which takes a second argument in which one places a boolean expression based on the above primitives and/or lockdep_is_held(). o A new kernel configuration parameter, CONFIG_PROVE_RCU, enables rcu_dereference_check(). This depends on CONFIG_PROVE_LOCKING, and should be quite helpful during the transition period while CONFIG_PROVE_RCU-unaware patches are in flight. The existing rcu_dereference() primitive does no checking, but upcoming patches will change that. Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1266887105-1528-1-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 126 +++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 116 insertions(+), 10 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 24440f4bf476..e3d37efe2703 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -78,14 +78,120 @@ extern void rcu_init(void); } while (0) #ifdef CONFIG_DEBUG_LOCK_ALLOC + extern struct lockdep_map rcu_lock_map; -# define rcu_read_acquire() \ - lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) +# define rcu_read_acquire() \ + lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) # define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_) -#else -# define rcu_read_acquire() do { } while (0) -# define rcu_read_release() do { } while (0) -#endif + +extern struct lockdep_map rcu_bh_lock_map; +# define rcu_read_acquire_bh() \ + lock_acquire(&rcu_bh_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) +# define rcu_read_release_bh() lock_release(&rcu_bh_lock_map, 1, _THIS_IP_) + +extern struct lockdep_map rcu_sched_lock_map; +# define rcu_read_acquire_sched() \ + lock_acquire(&rcu_sched_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) +# define rcu_read_release_sched() \ + lock_release(&rcu_sched_lock_map, 1, _THIS_IP_) + +/** + * rcu_read_lock_held - might we be in RCU read-side critical section? + * + * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in + * an RCU read-side critical section. In absence of CONFIG_PROVE_LOCKING, + * this assumes we are in an RCU read-side critical section unless it can + * prove otherwise. + */ +static inline int rcu_read_lock_held(void) +{ + if (debug_locks) + return lock_is_held(&rcu_lock_map); + return 1; +} + +/** + * rcu_read_lock_bh_held - might we be in RCU-bh read-side critical section? + * + * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in + * an RCU-bh read-side critical section. In absence of CONFIG_PROVE_LOCKING, + * this assumes we are in an RCU-bh read-side critical section unless it can + * prove otherwise. + */ +static inline int rcu_read_lock_bh_held(void) +{ + if (debug_locks) + return lock_is_held(&rcu_bh_lock_map); + return 1; +} + +/** + * rcu_read_lock_sched_held - might we be in RCU-sched read-side critical section? + * + * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in an + * RCU-sched read-side critical section. In absence of CONFIG_PROVE_LOCKING, + * this assumes we are in an RCU-sched read-side critical section unless it + * can prove otherwise. Note that disabling of preemption (including + * disabling irqs) counts as an RCU-sched read-side critical section. + */ +static inline int rcu_read_lock_sched_held(void) +{ + int lockdep_opinion = 0; + + if (debug_locks) + lockdep_opinion = lock_is_held(&rcu_sched_lock_map); + return lockdep_opinion || preempt_count() != 0; +} + +#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +# define rcu_read_acquire() do { } while (0) +# define rcu_read_release() do { } while (0) +# define rcu_read_acquire_bh() do { } while (0) +# define rcu_read_release_bh() do { } while (0) +# define rcu_read_acquire_sched() do { } while (0) +# define rcu_read_release_sched() do { } while (0) + +static inline int rcu_read_lock_held(void) +{ + return 1; +} + +static inline int rcu_read_lock_bh_held(void) +{ + return 1; +} + +static inline int rcu_read_lock_sched_held(void) +{ + return preempt_count() != 0; +} + +#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +#ifdef CONFIG_PROVE_RCU + +/** + * rcu_dereference_check - rcu_dereference with debug checking + * + * Do an rcu_dereference(), but check that the context is correct. + * For example, rcu_dereference_check(gp, rcu_read_lock_held()) to + * ensure that the rcu_dereference_check() executes within an RCU + * read-side critical section. It is also possible to check for + * locks being held, for example, by using lockdep_is_held(). + */ +#define rcu_dereference_check(p, c) \ + ({ \ + if (debug_locks) \ + WARN_ON_ONCE(!(c)); \ + rcu_dereference(p); \ + }) + +#else /* #ifdef CONFIG_PROVE_RCU */ + +#define rcu_dereference_check(p, c) rcu_dereference(p) + +#endif /* #else #ifdef CONFIG_PROVE_RCU */ /** * rcu_read_lock - mark the beginning of an RCU read-side critical section. @@ -160,7 +266,7 @@ static inline void rcu_read_lock_bh(void) { __rcu_read_lock_bh(); __acquire(RCU_BH); - rcu_read_acquire(); + rcu_read_acquire_bh(); } /* @@ -170,7 +276,7 @@ static inline void rcu_read_lock_bh(void) */ static inline void rcu_read_unlock_bh(void) { - rcu_read_release(); + rcu_read_release_bh(); __release(RCU_BH); __rcu_read_unlock_bh(); } @@ -188,7 +294,7 @@ static inline void rcu_read_lock_sched(void) { preempt_disable(); __acquire(RCU_SCHED); - rcu_read_acquire(); + rcu_read_acquire_sched(); } /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ @@ -205,7 +311,7 @@ static inline notrace void rcu_read_lock_sched_notrace(void) */ static inline void rcu_read_unlock_sched(void) { - rcu_read_release(); + rcu_read_release_sched(); __release(RCU_SCHED); preempt_enable(); } -- cgit v1.2.2 From c26d34a5858f96a564c45048bf5f09319d2abad1 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 22 Feb 2010 17:04:46 -0800 Subject: rcu: Add lockdep-enabled variants of rcu_dereference() Make rcu_dereference() check for being in an RCU read-side critical section, and create rcu_dereference_bh(), rcu_dereference_sched(), and srcu_dereference() to check for the other flavors of RCU. Also create rcu_dereference_raw() to avoid checking, and make rcu_dereference_check() use rcu_dereference_raw(). Acked-by: Eric Dumazet Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1266887105-1528-2-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 41 ++++++++++++++++++++++++++++++++++------- 1 file changed, 34 insertions(+), 7 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index e3d37efe2703..839d296a7ac0 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -184,12 +184,12 @@ static inline int rcu_read_lock_sched_held(void) ({ \ if (debug_locks) \ WARN_ON_ONCE(!(c)); \ - rcu_dereference(p); \ + rcu_dereference_raw(p); \ }) #else /* #ifdef CONFIG_PROVE_RCU */ -#define rcu_dereference_check(p, c) rcu_dereference(p) +#define rcu_dereference_check(p, c) rcu_dereference_raw(p) #endif /* #else #ifdef CONFIG_PROVE_RCU */ @@ -325,21 +325,48 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) /** - * rcu_dereference - fetch an RCU-protected pointer in an - * RCU read-side critical section. This pointer may later - * be safely dereferenced. + * rcu_dereference_raw - fetch an RCU-protected pointer + * + * The caller must be within some flavor of RCU read-side critical + * section, or must be otherwise preventing the pointer from changing, + * for example, by holding an appropriate lock. This pointer may later + * be safely dereferenced. It is the caller's responsibility to have + * done the right thing, as this primitive does no checking of any kind. * * Inserts memory barriers on architectures that require them * (currently only the Alpha), and, more importantly, documents * exactly which pointers are protected by RCU. */ - -#define rcu_dereference(p) ({ \ +#define rcu_dereference_raw(p) ({ \ typeof(p) _________p1 = ACCESS_ONCE(p); \ smp_read_barrier_depends(); \ (_________p1); \ }) +/** + * rcu_dereference - fetch an RCU-protected pointer, checking for RCU + * + * Makes rcu_dereference_check() do the dirty work. + */ +#define rcu_dereference(p) \ + rcu_dereference_check(p, rcu_read_lock_held()) + +/** + * rcu_dereference_bh - fetch an RCU-protected pointer, checking for RCU-bh + * + * Makes rcu_dereference_check() do the dirty work. + */ +#define rcu_dereference_bh(p) \ + rcu_dereference_check(p, rcu_read_lock_bh_held()) + +/** + * rcu_dereference_sched - fetch RCU-protected pointer, checking for RCU-sched + * + * Makes rcu_dereference_check() do the dirty work. + */ +#define rcu_dereference_sched(p) \ + rcu_dereference_check(p, rcu_read_lock_sched_held()) + /** * rcu_assign_pointer - assign (publicize) a pointer to a newly * initialized structure that will be dereferenced by RCU read-side -- cgit v1.2.2 From 0632eb3d7563d6a76d49a3860b6352d800c92854 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 22 Feb 2010 17:04:47 -0800 Subject: rcu: Integrate rcu_dereference_check() message into lockdep Make rcu_dereference_check() print the list of held locks in addition to the stack dump to ease debugging. Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1266887105-1528-3-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 839d296a7ac0..1a4de31bd7b4 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -182,8 +182,8 @@ static inline int rcu_read_lock_sched_held(void) */ #define rcu_dereference_check(p, c) \ ({ \ - if (debug_locks) \ - WARN_ON_ONCE(!(c)); \ + if (debug_locks && !(c)) \ + lockdep_rcu_dereference(__FILE__, __LINE__); \ rcu_dereference_raw(p); \ }) -- cgit v1.2.2 From d9f1bb6ad7fc53c406706f47858dd5ff030b14a3 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 25 Feb 2010 14:06:47 -0800 Subject: rcu: Make rcu_read_lock_sched_held() take boot time into account Before the scheduler starts, all tasks are non-preemptible by definition. So, during that time, rcu_read_lock_sched_held() needs to always return "true". This patch makes that be so. Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1267135607-7056-2-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 1a4de31bd7b4..fcea332a8424 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -62,6 +62,8 @@ extern int sched_expedited_torture_stats(char *page); /* Internal to kernel */ extern void rcu_init(void); +extern int rcu_scheduler_active; +extern void rcu_scheduler_starting(void); #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) #include @@ -140,7 +142,7 @@ static inline int rcu_read_lock_sched_held(void) if (debug_locks) lockdep_opinion = lock_is_held(&rcu_sched_lock_map); - return lockdep_opinion || preempt_count() != 0; + return lockdep_opinion || preempt_count() != 0 || !rcu_scheduler_active; } #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ -- cgit v1.2.2 From 0b1c87278a8c7e394022ec184a0b44a3886b6fde Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 26 Feb 2010 16:38:57 -0800 Subject: rcu: Make non-RCU_PROVE_LOCKING rcu_read_lock_sched_held() understand boot Before the scheduler starts, all tasks are non-preemptible by definition. So, during that time, rcu_read_lock_sched_held() needs to always return "true". This patch makes that be so for RCU_PROVE_LOCKING=n. Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1267231138-27856-2-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index fcea332a8424..c84373626336 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -166,7 +166,7 @@ static inline int rcu_read_lock_bh_held(void) static inline int rcu_read_lock_sched_held(void) { - return preempt_count() != 0; + return preempt_count() != 0 || !rcu_scheduler_active; } #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ -- cgit v1.2.2 From e6033e3b307fcfae08408e0673266db38392bda4 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 3 Mar 2010 17:50:16 -0800 Subject: rcu: Make rcu_read_lock_sched_held() handle !PREEMPT The rcu_read_lock_sched_held() needs to unconditionally return the value "1" in a !PREEMPT kernel, because under !PREEMPT, -all- kernel code is implicitly preempt-disabled. This patch makes this happen. Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1267667418-32233-1-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index c84373626336..e22960ecb71a 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -136,6 +136,7 @@ static inline int rcu_read_lock_bh_held(void) * can prove otherwise. Note that disabling of preemption (including * disabling irqs) counts as an RCU-sched read-side critical section. */ +#ifdef CONFIG_PREEMPT static inline int rcu_read_lock_sched_held(void) { int lockdep_opinion = 0; @@ -144,6 +145,12 @@ static inline int rcu_read_lock_sched_held(void) lockdep_opinion = lock_is_held(&rcu_sched_lock_map); return lockdep_opinion || preempt_count() != 0 || !rcu_scheduler_active; } +#else /* #ifdef CONFIG_PREEMPT */ +static inline int rcu_read_lock_sched_held(void) +{ + return 1; +} +#endif /* #else #ifdef CONFIG_PREEMPT */ #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ @@ -164,10 +171,17 @@ static inline int rcu_read_lock_bh_held(void) return 1; } +#ifdef CONFIG_PREEMPT static inline int rcu_read_lock_sched_held(void) { return preempt_count() != 0 || !rcu_scheduler_active; } +#else /* #ifdef CONFIG_PREEMPT */ +static inline int rcu_read_lock_sched_held(void) +{ + return 1; +} +#endif /* #else #ifdef CONFIG_PREEMPT */ #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ -- cgit v1.2.2 From 54dbf96c921513bf98484a20ef366d51944a4c4d Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 3 Mar 2010 07:46:57 -0800 Subject: rcu: Suppress RCU lockdep warnings during early boot RCU is used during very early boot, before RCU and lockdep have been initialized. So make the underlying primitives (rcu_read_lock_held(), rcu_read_lock_bh_held(), rcu_read_lock_sched_held(), and rcu_dereference_check()) check for early boot via the rcu_scheduler_active flag. This will suppress false positives. Also introduce a debug_lockdep_rcu_enabled() static inline helper function, which tags the CONTINUE_PROVE_RCU case as likely(), as suggested by Ingo Molnar. Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1267631219-8713-2-git-send-email-paulmck@linux.vnet.ibm.com> [ v2: removed incomplete debug_lockdep_rcu_update() bits ] Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 31 ++++++++++++++++++++++--------- 1 file changed, 22 insertions(+), 9 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index e22960ecb71a..75921b83c0ab 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -97,6 +97,11 @@ extern struct lockdep_map rcu_sched_lock_map; # define rcu_read_release_sched() \ lock_release(&rcu_sched_lock_map, 1, _THIS_IP_) +static inline int debug_lockdep_rcu_enabled(void) +{ + return likely(rcu_scheduler_active && debug_locks); +} + /** * rcu_read_lock_held - might we be in RCU read-side critical section? * @@ -104,12 +109,14 @@ extern struct lockdep_map rcu_sched_lock_map; * an RCU read-side critical section. In absence of CONFIG_PROVE_LOCKING, * this assumes we are in an RCU read-side critical section unless it can * prove otherwise. + * + * Check rcu_scheduler_active to prevent false positives during boot. */ static inline int rcu_read_lock_held(void) { - if (debug_locks) - return lock_is_held(&rcu_lock_map); - return 1; + if (!debug_lockdep_rcu_enabled()) + return 1; + return lock_is_held(&rcu_lock_map); } /** @@ -119,12 +126,14 @@ static inline int rcu_read_lock_held(void) * an RCU-bh read-side critical section. In absence of CONFIG_PROVE_LOCKING, * this assumes we are in an RCU-bh read-side critical section unless it can * prove otherwise. + * + * Check rcu_scheduler_active to prevent false positives during boot. */ static inline int rcu_read_lock_bh_held(void) { - if (debug_locks) - return lock_is_held(&rcu_bh_lock_map); - return 1; + if (!debug_lockdep_rcu_enabled()) + return 1; + return lock_is_held(&rcu_bh_lock_map); } /** @@ -135,15 +144,19 @@ static inline int rcu_read_lock_bh_held(void) * this assumes we are in an RCU-sched read-side critical section unless it * can prove otherwise. Note that disabling of preemption (including * disabling irqs) counts as an RCU-sched read-side critical section. + * + * Check rcu_scheduler_active to prevent false positives during boot. */ #ifdef CONFIG_PREEMPT static inline int rcu_read_lock_sched_held(void) { int lockdep_opinion = 0; + if (!debug_lockdep_rcu_enabled()) + return 1; if (debug_locks) lockdep_opinion = lock_is_held(&rcu_sched_lock_map); - return lockdep_opinion || preempt_count() != 0 || !rcu_scheduler_active; + return lockdep_opinion || preempt_count() != 0; } #else /* #ifdef CONFIG_PREEMPT */ static inline int rcu_read_lock_sched_held(void) @@ -174,7 +187,7 @@ static inline int rcu_read_lock_bh_held(void) #ifdef CONFIG_PREEMPT static inline int rcu_read_lock_sched_held(void) { - return preempt_count() != 0 || !rcu_scheduler_active; + return !rcu_scheduler_active || preempt_count() != 0; } #else /* #ifdef CONFIG_PREEMPT */ static inline int rcu_read_lock_sched_held(void) @@ -198,7 +211,7 @@ static inline int rcu_read_lock_sched_held(void) */ #define rcu_dereference_check(p, c) \ ({ \ - if (debug_locks && !(c)) \ + if (debug_lockdep_rcu_enabled() && !(c)) \ lockdep_rcu_dereference(__FILE__, __LINE__); \ rcu_dereference_raw(p); \ }) -- cgit v1.2.2 From e5ab67726f33b50f40db0ccf271ceb3c658554d5 Mon Sep 17 00:00:00 2001 From: Dave Young Date: Wed, 10 Mar 2010 15:24:05 -0800 Subject: sysctl extern cleanup: rcu Extern declarations in sysctl.c should be moved to their own header file, and then include them in relavant .c files. Move rcutorture_runnable extern declaration to linux/rcupdate.h Signed-off-by: Dave Young Acked-by: Josh Triplett Reviewed-by: "Paul E. McKenney" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/rcupdate.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index c84373626336..a005cac5e302 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -41,6 +41,10 @@ #include #include +#ifdef CONFIG_RCU_TORTURE_TEST +extern int rcutorture_runnable; /* for sysctl */ +#endif /* #ifdef CONFIG_RCU_TORTURE_TEST */ + /** * struct rcu_head - callback structure for use with RCU * @next: next update requests in a list -- cgit v1.2.2 From e3818b8dce2a934cd1521dbc4827e5238d8f45d8 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 15 Mar 2010 17:03:43 -0700 Subject: rcu: Make rcu_read_lock_bh_held() allow for disabled BH Disabling BH can stand in for rcu_read_lock_bh(), and this patch updates rcu_read_lock_bh_held() to allow for this. In order to avoid include-file hell, this function is moved out of line to kernel/rcupdate.c. This fixes a false positive RCU warning. Reported-by: Arnd Bergmann Reported-by: Eric Dumazet Signed-off-by: Paul E. McKenney Acked-by: Lai Jiangshan Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <20100316000343.GA25857@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 19 ++++--------------- 1 file changed, 4 insertions(+), 15 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 3024050c82a1..e1bdc4bfd275 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -123,22 +123,11 @@ static inline int rcu_read_lock_held(void) return lock_is_held(&rcu_lock_map); } -/** - * rcu_read_lock_bh_held - might we be in RCU-bh read-side critical section? - * - * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in - * an RCU-bh read-side critical section. In absence of CONFIG_PROVE_LOCKING, - * this assumes we are in an RCU-bh read-side critical section unless it can - * prove otherwise. - * - * Check rcu_scheduler_active to prevent false positives during boot. +/* + * rcu_read_lock_bh_held() is defined out of line to avoid #include-file + * hell. */ -static inline int rcu_read_lock_bh_held(void) -{ - if (!debug_lockdep_rcu_enabled()) - return 1; - return lock_is_held(&rcu_bh_lock_map); -} +extern int rcu_read_lock_bh_held(void); /** * rcu_read_lock_sched_held - might we be in RCU-sched read-side critical section? -- cgit v1.2.2 From 0cff810f54b3b52075c27f7a7021d5b195264b6c Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Thu, 18 Mar 2010 12:25:33 -0700 Subject: rcu: Fix local_irq_disable() CONFIG_PROVE_RCU=y false positives It is documented that local_irq_disable() also delimits RCU_SCHED read-site critical sections. See the document of synchronize_sched() or Documentation/RCU/whatisRCU.txt. So we have to test irqs_disabled() in rcu_read_lock_sched_held(). Otherwise rcu-lockdep brings incorrect complaint. Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com Cc: eric.dumazet@gmail.com LKML-Reference: <1268940334-10892-1-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index e1bdc4bfd275..872a98e13d6a 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -149,7 +149,7 @@ static inline int rcu_read_lock_sched_held(void) return 1; if (debug_locks) lockdep_opinion = lock_is_held(&rcu_sched_lock_map); - return lockdep_opinion || preempt_count() != 0; + return lockdep_opinion || preempt_count() != 0 || irqs_disabled(); } #else /* #ifdef CONFIG_PREEMPT */ static inline int rcu_read_lock_sched_held(void) @@ -180,7 +180,7 @@ static inline int rcu_read_lock_bh_held(void) #ifdef CONFIG_PREEMPT static inline int rcu_read_lock_sched_held(void) { - return !rcu_scheduler_active || preempt_count() != 0; + return !rcu_scheduler_active || preempt_count() != 0 || irqs_disabled(); } #else /* #ifdef CONFIG_PREEMPT */ static inline int rcu_read_lock_sched_held(void) -- cgit v1.2.2 From b62730baea32f86fe91a7930e4b7ee8d82778b79 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 9 Apr 2010 15:39:10 -0700 Subject: rcu: Add rcu_access_pointer and rcu_dereference_protected This patch adds variants of rcu_dereference() that handle situations where the RCU-protected data structure cannot change, perhaps due to our holding the update-side lock, or where the RCU-protected pointer is only to be fetched, not dereferenced. These are needed due to some performance concerns with using rcu_dereference() where it is not required, aside from the need for lockdep/sparse checking. The new rcu_access_pointer() primitive is for the case where the pointer is be fetch and not dereferenced. This primitive may be used without protection, RCU or otherwise, due to the fact that it uses ACCESS_ONCE(). The new rcu_dereference_protected() primitive is for the case where updates are prevented, for example, due to holding the update-side lock. This primitive does neither ACCESS_ONCE() nor smp_read_barrier_depends(), so can only be used when updates are somehow prevented. Suggested-by: David Howells Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com Cc: eric.dumazet@gmail.com LKML-Reference: <1270852752-25278-1-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 872a98e13d6a..8fe86609441f 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -209,12 +209,44 @@ static inline int rcu_read_lock_sched_held(void) rcu_dereference_raw(p); \ }) +/** + * rcu_dereference_protected - fetch RCU pointer when updates prevented + * + * Return the value of the specified RCU-protected pointer, but omit + * both the smp_read_barrier_depends() and the ACCESS_ONCE(). This + * is useful in cases where update-side locks prevent the value of the + * pointer from changing. Please note that this primitive does -not- + * prevent the compiler from repeating this reference or combining it + * with other references, so it should not be used without protection + * of appropriate locks. + */ +#define rcu_dereference_protected(p, c) \ + ({ \ + if (debug_lockdep_rcu_enabled() && !(c)) \ + lockdep_rcu_dereference(__FILE__, __LINE__); \ + (p); \ + }) + #else /* #ifdef CONFIG_PROVE_RCU */ #define rcu_dereference_check(p, c) rcu_dereference_raw(p) +#define rcu_dereference_protected(p, c) (p) #endif /* #else #ifdef CONFIG_PROVE_RCU */ +/** + * rcu_access_pointer - fetch RCU pointer with no dereferencing + * + * Return the value of the specified RCU-protected pointer, but omit the + * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful + * when the value of this pointer is accessed, but the pointer is not + * dereferenced, for example, when testing an RCU-protected pointer against + * NULL. This may also be used in cases where update-side locks prevent + * the value of the pointer from changing, but rcu_dereference_protected() + * is a lighter-weight primitive for this use case. + */ +#define rcu_access_pointer(p) ACCESS_ONCE(p) + /** * rcu_read_lock - mark the beginning of an RCU read-side critical section. * -- cgit v1.2.2 From c08c68dd76bd6b776bc0eb45a5e8f354ed772cdf Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 9 Apr 2010 15:39:11 -0700 Subject: rcu: Better explain the condition parameter of rcu_dereference_check() Better explain the condition parameter of rcu_dereference_check() that describes the conditions under which the dereference is permitted to take place (and incorporate Yong Zhang's suggestion). This condition is only checked under lockdep proving. Signed-off-by: David Howells Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: eric.dumazet@gmail.com LKML-Reference: <1270852752-25278-2-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 28 +++++++++++++++++++++++----- 1 file changed, 23 insertions(+), 5 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 8fe86609441f..9f1ddfef84b5 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -195,12 +195,30 @@ static inline int rcu_read_lock_sched_held(void) /** * rcu_dereference_check - rcu_dereference with debug checking + * @p: The pointer to read, prior to dereferencing + * @c: The conditions under which the dereference will take place * - * Do an rcu_dereference(), but check that the context is correct. - * For example, rcu_dereference_check(gp, rcu_read_lock_held()) to - * ensure that the rcu_dereference_check() executes within an RCU - * read-side critical section. It is also possible to check for - * locks being held, for example, by using lockdep_is_held(). + * Do an rcu_dereference(), but check that the conditions under which the + * dereference will take place are correct. Typically the conditions indicate + * the various locking conditions that should be held at that point. The check + * should return true if the conditions are satisfied. + * + * For example: + * + * bar = rcu_dereference_check(foo->bar, rcu_read_lock_held() || + * lockdep_is_held(&foo->lock)); + * + * could be used to indicate to lockdep that foo->bar may only be dereferenced + * if either the RCU read lock is held, or that the lock required to replace + * the bar struct at foo->bar is held. + * + * Note that the list of conditions may also include indications of when a lock + * need not be held, for example during initialisation or destruction of the + * target struct: + * + * bar = rcu_dereference_check(foo->bar, rcu_read_lock_held() || + * lockdep_is_held(&foo->lock) || + * atomic_read(&foo->usage) == 0); */ #define rcu_dereference_check(p, c) \ ({ \ -- cgit v1.2.2 From bc293d62b26ec590afc90a9e0a31c45d355b7bd8 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 15 Apr 2010 12:50:39 -0700 Subject: rcu: Make RCU lockdep check the lockdep_recursion variable The lockdep facility temporarily disables lockdep checking by incrementing the current->lockdep_recursion variable. Such disabling happens in NMIs and in other situations where lockdep might expect to recurse on itself. This patch therefore checks current->lockdep_recursion, disabling RCU lockdep splats when this variable is non-zero. In addition, this patch removes the "likely()", as suggested by Lai Jiangshan. Reported-by: Frederic Weisbecker Reported-by: David Miller Tested-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com Cc: eric.dumazet@gmail.com LKML-Reference: <20100415195039.GA22623@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 9f1ddfef84b5..07db2feb8572 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -101,10 +101,7 @@ extern struct lockdep_map rcu_sched_lock_map; # define rcu_read_release_sched() \ lock_release(&rcu_sched_lock_map, 1, _THIS_IP_) -static inline int debug_lockdep_rcu_enabled(void) -{ - return likely(rcu_scheduler_active && debug_locks); -} +extern int debug_lockdep_rcu_enabled(void); /** * rcu_read_lock_held - might we be in RCU read-side critical section? -- cgit v1.2.2 From ee84b8243b07c33a5c8aed42b4b2da60cb16d1d2 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 6 May 2010 09:28:41 -0700 Subject: rcu: create rcu_my_thread_group_empty() wrapper Some RCU-lockdep splat repairs need to know whether they are running in a single-threaded process. Unfortunately, the thread_group_empty() primitive is defined in sched.h, and can induce #include hell. This commit therefore introduces a rcu_my_thread_group_empty() wrapper that is defined in rcupdate.c, thus avoiding the need to include sched.h everywhere. Signed-off-by: "Paul E. McKenney" --- include/linux/rcupdate.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 07db2feb8572..db266bbed23f 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -190,6 +190,8 @@ static inline int rcu_read_lock_sched_held(void) #ifdef CONFIG_PROVE_RCU +extern int rcu_my_thread_group_empty(void); + /** * rcu_dereference_check - rcu_dereference with debug checking * @p: The pointer to read, prior to dereferencing -- cgit v1.2.2 From 2b3fc35f6919344e3cf722dde8308f47235c0b70 Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Tue, 20 Apr 2010 16:23:07 +0800 Subject: rcu: optionally leave lockdep enabled after RCU lockdep splat There is no need to disable lockdep after an RCU lockdep splat, so remove the debug_lockdeps_off() from lockdep_rcu_dereference(). To avoid repeated lockdep splats, use a static variable in the inlined rcu_dereference_check() and rcu_dereference_protected() macros so that a given instance splats only once, but so that multiple instances can be detected per boot. This is controlled by a new config variable CONFIG_PROVE_RCU_REPEATEDLY, which is disabled by default. This provides the normal lockdep behavior by default, but permits people who want to find multiple RCU-lockdep splats per boot to easily do so. Requested-by: Eric Paris Signed-off-by: Lai Jiangshan Tested-by: Eric Paris Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index db266bbed23f..4dca2752cfde 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -192,6 +192,15 @@ static inline int rcu_read_lock_sched_held(void) extern int rcu_my_thread_group_empty(void); +#define __do_rcu_dereference_check(c) \ + do { \ + static bool __warned; \ + if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \ + __warned = true; \ + lockdep_rcu_dereference(__FILE__, __LINE__); \ + } \ + } while (0) + /** * rcu_dereference_check - rcu_dereference with debug checking * @p: The pointer to read, prior to dereferencing @@ -221,8 +230,7 @@ extern int rcu_my_thread_group_empty(void); */ #define rcu_dereference_check(p, c) \ ({ \ - if (debug_lockdep_rcu_enabled() && !(c)) \ - lockdep_rcu_dereference(__FILE__, __LINE__); \ + __do_rcu_dereference_check(c); \ rcu_dereference_raw(p); \ }) @@ -239,8 +247,7 @@ extern int rcu_my_thread_group_empty(void); */ #define rcu_dereference_protected(p, c) \ ({ \ - if (debug_lockdep_rcu_enabled() && !(c)) \ - lockdep_rcu_dereference(__FILE__, __LINE__); \ + __do_rcu_dereference_check(c); \ (p); \ }) -- cgit v1.2.2 From d20200b591f59847ab6a5c23507084a7d29e23c5 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 30 Mar 2010 10:52:21 -0700 Subject: rcu: Fix bogus CONFIG_PROVE_LOCKING in comments to reflect reality. It is CONFIG_DEBUG_LOCK_ALLOC rather than CONFIG_PROVE_LOCKING, so fix it. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 4dca2752cfde..a150af0e5cd5 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -106,8 +106,8 @@ extern int debug_lockdep_rcu_enabled(void); /** * rcu_read_lock_held - might we be in RCU read-side critical section? * - * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in - * an RCU read-side critical section. In absence of CONFIG_PROVE_LOCKING, + * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU + * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, * this assumes we are in an RCU read-side critical section unless it can * prove otherwise. * @@ -129,11 +129,12 @@ extern int rcu_read_lock_bh_held(void); /** * rcu_read_lock_sched_held - might we be in RCU-sched read-side critical section? * - * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in an - * RCU-sched read-side critical section. In absence of CONFIG_PROVE_LOCKING, - * this assumes we are in an RCU-sched read-side critical section unless it - * can prove otherwise. Note that disabling of preemption (including - * disabling irqs) counts as an RCU-sched read-side critical section. + * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an + * RCU-sched read-side critical section. In absence of + * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side + * critical section unless it can prove otherwise. Note that disabling + * of preemption (including disabling irqs) counts as an RCU-sched + * read-side critical section. * * Check rcu_scheduler_active to prevent false positives during boot. */ -- cgit v1.2.2 From 32c141a0a1dfa29e0a07d78bec0c0919fc4b9f88 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 30 Mar 2010 10:59:28 -0700 Subject: rcu: fix now-bogus rcu_scheduler_active comments. The rcu_scheduler_active check has been wrapped into the new debug_lockdep_rcu_enabled() function, so update the comments to reflect this new reality. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index a150af0e5cd5..02537a72aaa4 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -111,7 +111,8 @@ extern int debug_lockdep_rcu_enabled(void); * this assumes we are in an RCU read-side critical section unless it can * prove otherwise. * - * Check rcu_scheduler_active to prevent false positives during boot. + * Check debug_lockdep_rcu_enabled() to prevent false positives during boot + * and while lockdep is disabled. */ static inline int rcu_read_lock_held(void) { @@ -136,7 +137,8 @@ extern int rcu_read_lock_bh_held(void); * of preemption (including disabling irqs) counts as an RCU-sched * read-side critical section. * - * Check rcu_scheduler_active to prevent false positives during boot. + * Check debug_lockdep_rcu_enabled() to prevent false positives during boot + * and while lockdep is disabled. */ #ifdef CONFIG_PREEMPT static inline int rcu_read_lock_sched_held(void) -- cgit v1.2.2 From da848c47bc6e873a54a445ea1960423a495b6b32 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 30 Mar 2010 15:46:01 -0700 Subject: rcu: shrink rcutiny by making synchronize_rcu_bh() be inline Because synchronize_rcu_bh() is identical to synchronize_sched(), make the former a static inline invoking the latter, saving the overhead of an EXPORT_SYMBOL_GPL() and the duplicate code. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 2 -- 1 file changed, 2 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 02537a72aaa4..d8fb2abcf303 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -56,8 +56,6 @@ struct rcu_head { }; /* Exported common interfaces */ -extern void synchronize_rcu_bh(void); -extern void synchronize_sched(void); extern void rcu_barrier(void); extern void rcu_barrier_bh(void); extern void rcu_barrier_sched(void); -- cgit v1.2.2 From bbad937983147c017c25406860287cb94da9af7c Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 2 Apr 2010 16:17:17 -0700 Subject: rcu: slim down rcutiny by removing rcu_scheduler_active and friends TINY_RCU does not need rcu_scheduler_active unless CONFIG_DEBUG_LOCK_ALLOC. So conditionally compile rcu_scheduler_active in order to slim down rcutiny a bit more. Also gets rid of an EXPORT_SYMBOL_GPL, which is responsible for most of the slimming. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index d8fb2abcf303..23be3a702516 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -64,8 +64,6 @@ extern int sched_expedited_torture_stats(char *page); /* Internal to kernel */ extern void rcu_init(void); -extern int rcu_scheduler_active; -extern void rcu_scheduler_starting(void); #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) #include @@ -178,7 +176,7 @@ static inline int rcu_read_lock_bh_held(void) #ifdef CONFIG_PREEMPT static inline int rcu_read_lock_sched_held(void) { - return !rcu_scheduler_active || preempt_count() != 0 || irqs_disabled(); + return preempt_count() != 0 || irqs_disabled(); } #else /* #ifdef CONFIG_PREEMPT */ static inline int rcu_read_lock_sched_held(void) -- cgit v1.2.2 From 4376030a54860dedab9d848dfa7cc700a6025c0b Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Sat, 17 Apr 2010 08:48:39 -0400 Subject: rcu head introduce rcu head init on stack PEM: o Would it be possible to make this bisectable as follows? a. Insert a new patch after current patch 4/6 that defines destroy_rcu_head_on_stack(), init_rcu_head_on_stack(), and init_rcu_head() with their !CONFIG_DEBUG_OBJECTS_RCU_HEAD definitions. This patch performs this transition. Signed-off-by: Mathieu Desnoyers CC: "Paul E. McKenney" CC: David S. Miller CC: akpm@linux-foundation.org CC: mingo@elte.hu CC: laijs@cn.fujitsu.com CC: dipankar@in.ibm.com CC: josh@joshtriplett.org CC: dvhltc@us.ibm.com CC: niv@us.ibm.com CC: tglx@linutronix.de CC: peterz@infradead.org CC: rostedt@goodmis.org CC: Valdis.Kletnieks@vt.edu CC: dhowells@redhat.com CC: eric.dumazet@gmail.com CC: Alexey Dobriyan Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 23be3a702516..b653b4aaa8a6 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -79,6 +79,14 @@ extern void rcu_init(void); (ptr)->next = NULL; (ptr)->func = NULL; \ } while (0) +static inline void init_rcu_head_on_stack(struct rcu_head *head) +{ +} + +static inline void destroy_rcu_head_on_stack(struct rcu_head *head) +{ +} + #ifdef CONFIG_DEBUG_LOCK_ALLOC extern struct lockdep_map rcu_lock_map; -- cgit v1.2.2 From 551d55a944b143ef26fbd482d1c463199d6f65cf Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Sat, 17 Apr 2010 08:48:42 -0400 Subject: tree/tiny rcu: Add debug RCU head objects Helps finding racy users of call_rcu(), which results in hangs because list entries are overwritten and/or skipped. Changelog since v4: - Bissectability is now OK - Now generate a WARN_ON_ONCE() for non-initialized rcu_head passed to call_rcu(). Statically initialized objects are detected with object_is_static(). - Rename rcu_head_init_on_stack to init_rcu_head_on_stack. - Remove init_rcu_head() completely. Changelog since v3: - Include comments from Lai Jiangshan This new patch version is based on the debugobjects with the newly introduced "active state" tracker. Non-initialized entries are all considered as "statically initialized". An activation fixup (triggered by call_rcu()) takes care of performing the debug object initialization without issuing any warning. Since we cannot increase the size of struct rcu_head, I don't see much room to put an identifier for statically initialized rcu_head structures. So for now, we have to live without "activation without explicit init" detection. But the main purpose of this debug option is to detect double-activations (double call_rcu() use of a rcu_head before the callback is executed), which is correctly addressed here. This also detects potential internal RCU callback corruption, which would cause the callbacks to be executed twice. Signed-off-by: Mathieu Desnoyers CC: David S. Miller CC: "Paul E. McKenney" CC: akpm@linux-foundation.org CC: mingo@elte.hu CC: laijs@cn.fujitsu.com CC: dipankar@in.ibm.com CC: josh@joshtriplett.org CC: dvhltc@us.ibm.com CC: niv@us.ibm.com CC: tglx@linutronix.de CC: peterz@infradead.org CC: rostedt@goodmis.org CC: Valdis.Kletnieks@vt.edu CC: dhowells@redhat.com CC: eric.dumazet@gmail.com CC: Alexey Dobriyan Signed-off-by: Paul E. McKenney Reviewed-by: Lai Jiangshan --- include/linux/rcupdate.h | 49 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 49 insertions(+) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index b653b4aaa8a6..2b7fc506e479 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -40,6 +40,7 @@ #include #include #include +#include #ifdef CONFIG_RCU_TORTURE_TEST extern int rcutorture_runnable; /* for sysctl */ @@ -79,6 +80,16 @@ extern void rcu_init(void); (ptr)->next = NULL; (ptr)->func = NULL; \ } while (0) +/* + * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic + * initialization and destruction of rcu_head on the stack. rcu_head structures + * allocated dynamically in the heap or defined statically don't need any + * initialization. + */ +#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD +extern void init_rcu_head_on_stack(struct rcu_head *head); +extern void destroy_rcu_head_on_stack(struct rcu_head *head); +#else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ static inline void init_rcu_head_on_stack(struct rcu_head *head) { } @@ -86,6 +97,7 @@ static inline void init_rcu_head_on_stack(struct rcu_head *head) static inline void destroy_rcu_head_on_stack(struct rcu_head *head) { } +#endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ #ifdef CONFIG_DEBUG_LOCK_ALLOC @@ -517,4 +529,41 @@ extern void call_rcu(struct rcu_head *head, extern void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *head)); +/* + * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally + * by call_rcu() and rcu callback execution, and are therefore not part of the + * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors. + */ + +#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD +# define STATE_RCU_HEAD_READY 0 +# define STATE_RCU_HEAD_QUEUED 1 + +extern struct debug_obj_descr rcuhead_debug_descr; + +static inline void debug_rcu_head_queue(struct rcu_head *head) +{ + debug_object_activate(head, &rcuhead_debug_descr); + debug_object_active_state(head, &rcuhead_debug_descr, + STATE_RCU_HEAD_READY, + STATE_RCU_HEAD_QUEUED); +} + +static inline void debug_rcu_head_unqueue(struct rcu_head *head) +{ + debug_object_active_state(head, &rcuhead_debug_descr, + STATE_RCU_HEAD_QUEUED, + STATE_RCU_HEAD_READY); + debug_object_deactivate(head, &rcuhead_debug_descr); +} +#else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ +static inline void debug_rcu_head_queue(struct rcu_head *head) +{ +} + +static inline void debug_rcu_head_unqueue(struct rcu_head *head) +{ +} +#endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ + #endif /* __LINUX_RCUPDATE_H */ -- cgit v1.2.2 From f5155b33277c9678041a27869165619bb34f722f Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 30 Apr 2010 06:42:01 -0700 Subject: rcu: add an rcu_dereference_index_check() The sparse RCU-pointer checking relies on type magic that dereferences the pointer in question. This does not work if the pointer is in fact an array index. This commit therefore supplies a new RCU API that omits the sparse checking to continue to support rcu_dereference() on integers. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 2b7fc506e479..9fbc54a2585d 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -566,4 +566,37 @@ static inline void debug_rcu_head_unqueue(struct rcu_head *head) } #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ +#ifndef CONFIG_PROVE_RCU +#define __do_rcu_dereference_check(c) do { } while (0) +#endif /* #ifdef CONFIG_PROVE_RCU */ + +#define __rcu_dereference_index_check(p, c) \ + ({ \ + typeof(p) _________p1 = ACCESS_ONCE(p); \ + __do_rcu_dereference_check(c); \ + smp_read_barrier_depends(); \ + (_________p1); \ + }) + +/** + * rcu_dereference_index_check() - rcu_dereference for indices with debug checking + * @p: The pointer to read, prior to dereferencing + * @c: The conditions under which the dereference will take place + * + * Similar to rcu_dereference_check(), but omits the sparse checking. + * This allows rcu_dereference_index_check() to be used on integers, + * which can then be used as array indices. Attempting to use + * rcu_dereference_check() on an integer will give compiler warnings + * because the sparse address-space mechanism relies on dereferencing + * the RCU-protected pointer. Dereferencing integers is not something + * that even gcc will put up with. + * + * Note that this function does not implicitly check for RCU read-side + * critical sections. If this function gains lots of uses, it might + * make sense to provide versions for each flavor of RCU, but it does + * not make sense as of early 2010. + */ +#define rcu_dereference_index_check(p, c) \ + __rcu_dereference_index_check((p), (c)) + #endif /* __LINUX_RCUPDATE_H */ -- cgit v1.2.2 From b3a084b9b684622b149e8dcf03855bf0d5fb588b Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 22 Sep 2010 08:38:44 +0200 Subject: rcu: rcu_read_lock_bh_held(): disabling irqs also disables bh rcu_dereference_bh() doesnt know yet about hard irq being disabled, so lockdep can trigger in netpoll_rx() after commit f0f9deae9e7c4 (netpoll: Disable IRQ around RCU dereference in netpoll_rx) Reported-by: Miles Lane Signed-off-by: Eric Dumazet Tested-by: Miles Lane Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 9fbc54a2585d..83af1f8d8b74 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -454,7 +454,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) * Makes rcu_dereference_check() do the dirty work. */ #define rcu_dereference_bh(p) \ - rcu_dereference_check(p, rcu_read_lock_bh_held()) + rcu_dereference_check(p, rcu_read_lock_bh_held() || irqs_disabled()) /** * rcu_dereference_sched - fetch RCU-protected pointer, checking for RCU-sched -- cgit v1.2.2