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Commit ff195cb69ba8d2af9b891be3a26db95fe1999d43

Authored by Paul E. McKenney
Committed by Paul E. McKenney
1 parent d8ab29f8be
Exists in master and in 6 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

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>

Showing 1 changed file with 23 additions and 13 deletions Side-by-side Diff

include/linux/srcu.h
Diff comments   View file @ ff195cb
... ... @@ -28,6 +28,7 @@
28 28 #define _LINUX_SRCU_H
29 29  
30 30 #include <linux/mutex.h>
  31 +#include <linux/rcupdate.h>
31 32  
32 33 struct srcu_struct_array {
33 34 int c[2];
34 35  
... ... @@ -60,18 +61,10 @@
60 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 64 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
69 65  
70 66 int 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 68 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
76 69  
77 70 void cleanup_srcu_struct(struct srcu_struct *sp);
78 71  
... ... @@ -90,12 +83,29 @@
90 83 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
91 84 * this assumes we are in an SRCU read-side critical section unless it can
92 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 */
94 100 static inline int srcu_read_lock_held(struct srcu_struct *sp)
95 101 {
96   - if (debug_locks)
97   - return lock_is_held(&sp->dep_map);
98   - return 1;
  102 + if (rcu_is_cpu_idle())
  103 + return 0;
  104 +
  105 + if (!debug_locks)
  106 + return 1;
  107 +
  108 + return lock_is_held(&sp->dep_map);
99 109 }
100 110  
101 111 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
... ... @@ -150,7 +160,7 @@
150 160 {
151 161 int retval = __srcu_read_lock(sp);
152 162  
153   - srcu_read_acquire(sp);
  163 + rcu_lock_acquire(&(sp)->dep_map);
154 164 return retval;
155 165 }
156 166  
... ... @@ -164,7 +174,7 @@
164 174 static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
165 175 __releases(sp)
166 176 {
167   - srcu_read_release(sp);
  177 + rcu_lock_release(&(sp)->dep_map);
168 178 __srcu_read_unlock(sp, idx);
169 179 }
170 180