From 42d35d48ce7cefb9429880af19d1c329d1554e7a Mon Sep 17 00:00:00 2001 From: Darren Hart Date: Mon, 29 Dec 2008 15:49:53 -0800 Subject: futex: make futex_(get|put)_key() calls symmetric Impact: cleanup This patch makes the calls to futex_get_key_refs() and futex_drop_key_refs() explicitly symmetric by only "putting" keys we successfully "got". Also cleanup a couple return points that didn't "put" after a successful "get". Build and boot tested on an x86_64 system. Signed-off-by: Darren Hart Cc: Signed-off-by: Ingo Molnar --- kernel/futex.c | 67 +++++++++++++++++++++++++++++++--------------------------- 1 file changed, 36 insertions(+), 31 deletions(-) (limited to 'kernel') diff --git a/kernel/futex.c b/kernel/futex.c index b4f87bac91c..c5ac55cc0c1 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -723,8 +723,8 @@ static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset) } spin_unlock(&hb->lock); -out: put_futex_key(fshared, &key); +out: return ret; } @@ -748,7 +748,7 @@ retryfull: goto out; ret = get_futex_key(uaddr2, fshared, &key2); if (unlikely(ret != 0)) - goto out; + goto out_put_key1; hb1 = hash_futex(&key1); hb2 = hash_futex(&key2); @@ -770,12 +770,12 @@ retry: * but we might get them from range checking */ ret = op_ret; - goto out; + goto out_put_keys; #endif if (unlikely(op_ret != -EFAULT)) { ret = op_ret; - goto out; + goto out_put_keys; } /* @@ -789,7 +789,7 @@ retry: ret = futex_handle_fault((unsigned long)uaddr2, attempt); if (ret) - goto out; + goto out_put_keys; goto retry; } @@ -827,10 +827,11 @@ retry: spin_unlock(&hb1->lock); if (hb1 != hb2) spin_unlock(&hb2->lock); -out: +out_put_keys: put_futex_key(fshared, &key2); +out_put_key1: put_futex_key(fshared, &key1); - +out: return ret; } @@ -847,13 +848,13 @@ static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2, struct futex_q *this, *next; int ret, drop_count = 0; - retry: +retry: ret = get_futex_key(uaddr1, fshared, &key1); if (unlikely(ret != 0)) goto out; ret = get_futex_key(uaddr2, fshared, &key2); if (unlikely(ret != 0)) - goto out; + goto out_put_key1; hb1 = hash_futex(&key1); hb2 = hash_futex(&key2); @@ -875,7 +876,7 @@ static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2, if (!ret) goto retry; - return ret; + goto out_put_keys; } if (curval != *cmpval) { ret = -EAGAIN; @@ -920,9 +921,11 @@ out_unlock: while (--drop_count >= 0) drop_futex_key_refs(&key1); -out: +out_put_keys: put_futex_key(fshared, &key2); +out_put_key1: put_futex_key(fshared, &key1); +out: return ret; } @@ -983,7 +986,7 @@ static int unqueue_me(struct futex_q *q) int ret = 0; /* In the common case we don't take the spinlock, which is nice. */ - retry: +retry: lock_ptr = q->lock_ptr; barrier(); if (lock_ptr != NULL) { @@ -1165,11 +1168,11 @@ static int futex_wait(u32 __user *uaddr, int fshared, q.pi_state = NULL; q.bitset = bitset; - retry: +retry: q.key = FUTEX_KEY_INIT; ret = get_futex_key(uaddr, fshared, &q.key); if (unlikely(ret != 0)) - goto out_release_sem; + goto out; hb = queue_lock(&q); @@ -1197,6 +1200,7 @@ static int futex_wait(u32 __user *uaddr, int fshared, if (unlikely(ret)) { queue_unlock(&q, hb); + put_futex_key(fshared, &q.key); ret = get_user(uval, uaddr); @@ -1206,7 +1210,7 @@ static int futex_wait(u32 __user *uaddr, int fshared, } ret = -EWOULDBLOCK; if (uval != val) - goto out_unlock_release_sem; + goto out_unlock_put_key; /* Only actually queue if *uaddr contained val. */ queue_me(&q, hb); @@ -1298,11 +1302,11 @@ static int futex_wait(u32 __user *uaddr, int fshared, return -ERESTART_RESTARTBLOCK; } - out_unlock_release_sem: +out_unlock_put_key: queue_unlock(&q, hb); - - out_release_sem: put_futex_key(fshared, &q.key); + +out: return ret; } @@ -1351,16 +1355,16 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared, } q.pi_state = NULL; - retry: +retry: q.key = FUTEX_KEY_INIT; ret = get_futex_key(uaddr, fshared, &q.key); if (unlikely(ret != 0)) - goto out_release_sem; + goto out; - retry_unlocked: +retry_unlocked: hb = queue_lock(&q); - retry_locked: +retry_locked: ret = lock_taken = 0; /* @@ -1381,14 +1385,14 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared, */ if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) { ret = -EDEADLK; - goto out_unlock_release_sem; + goto out_unlock_put_key; } /* * Surprise - we got the lock. Just return to userspace: */ if (unlikely(!curval)) - goto out_unlock_release_sem; + goto out_unlock_put_key; uval = curval; @@ -1424,7 +1428,7 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared, * We took the lock due to owner died take over. */ if (unlikely(lock_taken)) - goto out_unlock_release_sem; + goto out_unlock_put_key; /* * We dont have the lock. Look up the PI state (or create it if @@ -1463,7 +1467,7 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared, goto retry_locked; } default: - goto out_unlock_release_sem; + goto out_unlock_put_key; } } @@ -1554,16 +1558,17 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared, destroy_hrtimer_on_stack(&to->timer); return ret != -EINTR ? ret : -ERESTARTNOINTR; - out_unlock_release_sem: +out_unlock_put_key: queue_unlock(&q, hb); - out_release_sem: +out_put_key: put_futex_key(fshared, &q.key); +out: if (to) destroy_hrtimer_on_stack(&to->timer); return ret; - uaddr_faulted: +uaddr_faulted: /* * We have to r/w *(int __user *)uaddr, and we have to modify it * atomically. Therefore, if we continue to fault after get_user() @@ -1576,7 +1581,7 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared, if (attempt++) { ret = futex_handle_fault((unsigned long)uaddr, attempt); if (ret) - goto out_release_sem; + goto out_put_key; goto retry_unlocked; } @@ -1668,9 +1673,9 @@ retry_unlocked: out_unlock: spin_unlock(&hb->lock); -out: put_futex_key(fshared, &key); +out: return ret; pi_faulted: -- cgit v1.2.2 From 90621c40cc4ab7b0a414311ce37e7cc7173403b6 Mon Sep 17 00:00:00 2001 From: Darren Hart Date: Mon, 29 Dec 2008 19:43:21 -0800 Subject: futex: catch certain assymetric (get|put)_futex_key calls Impact: add debug check Following up on my previous key reference accounting patches, this patch will catch puts on keys that haven't been "got". This won't catch nested get/put mismatches though. Build and boot tested, with minimal desktop activity and a run of the open_posix_testsuite in LTP for testing. No warnings logged. Signed-off-by: Darren Hart Cc: Signed-off-by: Ingo Molnar --- kernel/futex.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/futex.c b/kernel/futex.c index c5ac55cc0c1..206d4c90688 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -170,8 +170,11 @@ static void get_futex_key_refs(union futex_key *key) */ static void drop_futex_key_refs(union futex_key *key) { - if (!key->both.ptr) + if (!key->both.ptr) { + /* If we're here then we tried to put a key we failed to get */ + WARN_ON_ONCE(1); return; + } switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { case FUT_OFF_INODE: -- cgit v1.2.2 From c12172c0251761c54260376eb29a5f6547495580 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 4 Jan 2009 20:30:06 -0800 Subject: rcu: fix rcutree grace-period-latency bug on small systems Impact: fix delays during bootup Kudos to Andi Kleen for finding a grace-period-latency problem! The problem was that the special-case code for small machines never updated the ->signaled field to indicate that grace-period initialization had completed, which prevented force_quiescent_state() from ever expediting grace periods. This problem resulted in grace periods extending for more than 20 seconds. Not subtle. I introduced this bug during my inspection process when I fixed a race between grace-period initialization and force_quiescent_state() execution. The following patch properly updates the ->signaled field for the "small"-system case (no more than 32 CPUs for 32-bit kernels and no more than 64 CPUs for 64-bit kernels). Reported-by: Andi Kleen Tested-by: Andi Kleen Signed-off-by: Paul E. McKenney Signed-off-by: Ingo Molnar --- kernel/rcutree.c | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel') diff --git a/kernel/rcutree.c b/kernel/rcutree.c index a342b032112..88d921c5c44 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -572,6 +572,7 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags) /* Special-case the common single-level case. */ if (NUM_RCU_NODES == 1) { rnp->qsmask = rnp->qsmaskinit; + rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */ spin_unlock_irqrestore(&rnp->lock, flags); return; } -- cgit v1.2.2 From 90a4d2c0106bb690f0b6af3d506febc35c658aa7 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 4 Jan 2009 11:41:11 -0800 Subject: rcu: make treercu safe for suspend and resume Impact: fix kernel warnings [and potential crash] during suspend+resume Kudos to both Dhaval Giani and Jens Axboe for finding a bug in treercu that causes warnings after suspend-resume cycles in Dhaval's case and during stress tests in Jens's case. It would also probably cause failures if heavily stressed. The solution, ironically enough, is to revert to rcupreempt's code for initializing the dynticks state. And the patch even results in smaller code -- so what was I thinking??? This is 2.6.29 material, given that people really do suspend and resume Linux these days. ;-) Reported-by: Dhaval Giani Reported-by: Jens Axboe Tested-by: Dhaval Giani Tested-by: Jens Axboe Signed-off-by: Paul E. McKenney Signed-off-by: Ingo Molnar --- kernel/rcutree.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) (limited to 'kernel') diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 88d921c5c44..f2d8638e6c6 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -79,7 +79,10 @@ struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); #ifdef CONFIG_NO_HZ -DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks); +DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { + .dynticks_nesting = 1, + .dynticks = 1, +}; #endif /* #ifdef CONFIG_NO_HZ */ static int blimit = 10; /* Maximum callbacks per softirq. */ @@ -1380,13 +1383,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp) static void __cpuinit rcu_online_cpu(int cpu) { -#ifdef CONFIG_NO_HZ - struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); - - rdtp->dynticks_nesting = 1; - rdtp->dynticks |= 1; /* need consecutive #s even for hotplug. */ - rdtp->dynticks_nmi = (rdtp->dynticks_nmi + 1) & ~0x1; -#endif /* #ifdef CONFIG_NO_HZ */ rcu_init_percpu_data(cpu, &rcu_state); rcu_init_percpu_data(cpu, &rcu_bh_state); open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); -- cgit v1.2.2 From ea7d3fef4222cd98556a0b386598268d4dbf6670 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 4 Jan 2009 13:03:02 -0800 Subject: rcu: eliminate synchronize_rcu_xxx macro Impact: cleanup Expand macro into two files. The synchronize_rcu_xxx macro is quite ugly and it's only used by two callers, so expand it instead. This makes this code easier to change. Signed-off-by: Andi Kleen Signed-off-by: Paul E. McKenney Signed-off-by: Ingo Molnar --- kernel/rcupdate.c | 11 +++++++++-- kernel/rcupreempt.c | 11 ++++++++++- 2 files changed, 19 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index ad63af8b252..d92a76a881a 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -77,8 +77,15 @@ void wakeme_after_rcu(struct rcu_head *head) * sections are delimited by rcu_read_lock() and rcu_read_unlock(), * and may be nested. */ -void synchronize_rcu(void); /* Makes kernel-doc tools happy */ -synchronize_rcu_xxx(synchronize_rcu, call_rcu) +void synchronize_rcu(void) +{ + struct rcu_synchronize rcu; + init_completion(&rcu.completion); + /* Will wake me after RCU finished. */ + call_rcu(&rcu.head, wakeme_after_rcu); + /* Wait for it. */ + wait_for_completion(&rcu.completion); +} EXPORT_SYMBOL_GPL(synchronize_rcu); static void rcu_barrier_callback(struct rcu_head *notused) diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c index f9dc8f3720f..33cfc50781f 100644 --- a/kernel/rcupreempt.c +++ b/kernel/rcupreempt.c @@ -1177,7 +1177,16 @@ EXPORT_SYMBOL_GPL(call_rcu_sched); * in -rt this does -not- necessarily result in all currently executing * interrupt -handlers- having completed. */ -synchronize_rcu_xxx(__synchronize_sched, call_rcu_sched) +void __synchronize_sched(void) +{ + struct rcu_synchronize rcu; + + init_completion(&rcu.completion); + /* Will wake me after RCU finished. */ + call_rcu_sched(&rcu.head, wakeme_after_rcu); + /* Wait for it. */ + wait_for_completion(&rcu.completion); +} EXPORT_SYMBOL_GPL(__synchronize_sched); /* -- cgit v1.2.2 From c59ab97e9ecdee9084d2da09e5a8ceea9a396508 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 4 Jan 2009 18:28:27 -0800 Subject: rcu: fix rcutorture bug Fix an rcutorture bug that prevents the shutdown notifier from ever actually having any effect, due to the fact that kthreads ignore all signals. Signed-off-by: Paul E. McKenney Signed-off-by: Ingo Molnar --- kernel/rcutorture.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) (limited to 'kernel') diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c index 3245b40952c..1cff28db56b 100644 --- a/kernel/rcutorture.c +++ b/kernel/rcutorture.c @@ -136,7 +136,7 @@ static int stutter_pause_test = 0; #endif int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT; -#define FULLSTOP_SIGNALED 1 /* Bail due to signal. */ +#define FULLSTOP_SHUTDOWN 1 /* Bail due to system shutdown/panic. */ #define FULLSTOP_CLEANUP 2 /* Orderly shutdown. */ static int fullstop; /* stop generating callbacks at test end. */ DEFINE_MUTEX(fullstop_mutex); /* protect fullstop transitions and */ @@ -151,12 +151,10 @@ rcutorture_shutdown_notify(struct notifier_block *unused1, { if (fullstop) return NOTIFY_DONE; - if (signal_pending(current)) { - mutex_lock(&fullstop_mutex); - if (!ACCESS_ONCE(fullstop)) - fullstop = FULLSTOP_SIGNALED; - mutex_unlock(&fullstop_mutex); - } + mutex_lock(&fullstop_mutex); + if (!fullstop) + fullstop = FULLSTOP_SHUTDOWN; + mutex_unlock(&fullstop_mutex); return NOTIFY_DONE; } @@ -624,7 +622,7 @@ rcu_torture_writer(void *arg) rcu_stutter_wait(); } while (!kthread_should_stop() && !fullstop); VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping"); - while (!kthread_should_stop() && fullstop != FULLSTOP_SIGNALED) + while (!kthread_should_stop() && fullstop != FULLSTOP_SHUTDOWN) schedule_timeout_uninterruptible(1); return 0; } @@ -649,7 +647,7 @@ rcu_torture_fakewriter(void *arg) } while (!kthread_should_stop() && !fullstop); VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping"); - while (!kthread_should_stop() && fullstop != FULLSTOP_SIGNALED) + while (!kthread_should_stop() && fullstop != FULLSTOP_SHUTDOWN) schedule_timeout_uninterruptible(1); return 0; } @@ -759,7 +757,7 @@ rcu_torture_reader(void *arg) VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping"); if (irqreader && cur_ops->irqcapable) del_timer_sync(&t); - while (!kthread_should_stop() && fullstop != FULLSTOP_SIGNALED) + while (!kthread_should_stop() && fullstop != FULLSTOP_SHUTDOWN) schedule_timeout_uninterruptible(1); return 0; } -- cgit v1.2.2