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authorPaul E. McKenney <paul.mckenney@linaro.org>2011-10-07 12:22:04 -0400
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2011-12-11 13:31:33 -0500
commitff195cb69ba8d2af9b891be3a26db95fe1999d43 (patch)
treeb7e3071e87e8abdf998d4d6200228ef1a9c906d6
parentd8ab29f8be918b34a1ccd174569a53f0eb04b0a5 (diff)
rcu: Warn when srcu_read_lock() is used in an extended quiescent state
Catch SRCU up to the other variants of RCU by making PROVE_RCU complain if either srcu_read_lock() or srcu_read_lock_held() are used from within RCU-idle mode. Frederic reworked this to allow for the new versions of his patches that check for extended quiescent states. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
-rw-r--r--include/linux/srcu.h36
1 files changed, 23 insertions, 13 deletions
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 58971e891f48..4e0a3d41dae3 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -28,6 +28,7 @@
28#define _LINUX_SRCU_H 28#define _LINUX_SRCU_H
29 29
30#include <linux/mutex.h> 30#include <linux/mutex.h>
31#include <linux/rcupdate.h>
31 32
32struct srcu_struct_array { 33struct srcu_struct_array {
33 int c[2]; 34 int c[2];
@@ -60,18 +61,10 @@ int __init_srcu_struct(struct srcu_struct *sp, const char *name,
60 __init_srcu_struct((sp), #sp, &__srcu_key); \ 61 __init_srcu_struct((sp), #sp, &__srcu_key); \
61}) 62})
62 63
63# define srcu_read_acquire(sp) \
64 lock_acquire(&(sp)->dep_map, 0, 0, 2, 1, NULL, _THIS_IP_)
65# define srcu_read_release(sp) \
66 lock_release(&(sp)->dep_map, 1, _THIS_IP_)
67
68#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 64#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
69 65
70int init_srcu_struct(struct srcu_struct *sp); 66int init_srcu_struct(struct srcu_struct *sp);
71 67
72# define srcu_read_acquire(sp) do { } while (0)
73# define srcu_read_release(sp) do { } while (0)
74
75#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 68#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
76 69
77void cleanup_srcu_struct(struct srcu_struct *sp); 70void cleanup_srcu_struct(struct srcu_struct *sp);
@@ -90,12 +83,29 @@ long srcu_batches_completed(struct srcu_struct *sp);
90 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, 83 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
91 * this assumes we are in an SRCU read-side critical section unless it can 84 * this assumes we are in an SRCU read-side critical section unless it can
92 * prove otherwise. 85 * prove otherwise.
86 *
87 * Note that if the CPU is in the idle loop from an RCU point of view
88 * (ie: that we are in the section between rcu_idle_enter() and
89 * rcu_idle_exit()) then srcu_read_lock_held() returns false even if
90 * the CPU did an srcu_read_lock(). The reason for this is that RCU
91 * ignores CPUs that are in such a section, considering these as in
92 * extended quiescent state, so such a CPU is effectively never in an
93 * RCU read-side critical section regardless of what RCU primitives it
94 * invokes. This state of affairs is required --- we need to keep an
95 * RCU-free window in idle where the CPU may possibly enter into low
96 * power mode. This way we can notice an extended quiescent state to
97 * other CPUs that started a grace period. Otherwise we would delay any
98 * grace period as long as we run in the idle task.
93 */ 99 */
94static inline int srcu_read_lock_held(struct srcu_struct *sp) 100static inline int srcu_read_lock_held(struct srcu_struct *sp)
95{ 101{
96 if (debug_locks) 102 if (rcu_is_cpu_idle())
97 return lock_is_held(&sp->dep_map); 103 return 0;
98 return 1; 104
105 if (!debug_locks)
106 return 1;
107
108 return lock_is_held(&sp->dep_map);
99} 109}
100 110
101#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 111#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
@@ -150,7 +160,7 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
150{ 160{
151 int retval = __srcu_read_lock(sp); 161 int retval = __srcu_read_lock(sp);
152 162
153 srcu_read_acquire(sp); 163 rcu_lock_acquire(&(sp)->dep_map);
154 return retval; 164 return retval;
155} 165}
156 166
@@ -164,7 +174,7 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
164static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) 174static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
165 __releases(sp) 175 __releases(sp)
166{ 176{
167 srcu_read_release(sp); 177 rcu_lock_release(&(sp)->dep_map);
168 __srcu_read_unlock(sp, idx); 178 __srcu_read_unlock(sp, idx);
169} 179}
170 180