From c1f960b53e248bed01368dbbe1a68b64866b47ed Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 23 Jun 2011 20:48:04 -0700 Subject: [PATCH] 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 dyntick-idle mode. Signed-off-by: Paul E. McKenney --- include/linux/srcu.h | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 58971e891f48..fcbaee760234 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -28,6 +28,7 @@ #define _LINUX_SRCU_H #include +#include struct srcu_struct_array { int c[2]; @@ -60,18 +61,10 @@ int __init_srcu_struct(struct srcu_struct *sp, const char *name, __init_srcu_struct((sp), #sp, &__srcu_key); \ }) -# define srcu_read_acquire(sp) \ - lock_acquire(&(sp)->dep_map, 0, 0, 2, 1, NULL, _THIS_IP_) -# define srcu_read_release(sp) \ - lock_release(&(sp)->dep_map, 1, _THIS_IP_) - #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ int init_srcu_struct(struct srcu_struct *sp); -# define srcu_read_acquire(sp) do { } while (0) -# define srcu_read_release(sp) do { } while (0) - #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ void cleanup_srcu_struct(struct srcu_struct *sp); @@ -90,11 +83,23 @@ long srcu_batches_completed(struct srcu_struct *sp); * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, * this assumes we are in an SRCU read-side critical section unless it can * prove otherwise. + * + * Note that if the CPU is in an extended quiescent state, for example, + * if the CPU is in dyntick-idle mode, then rcu_read_lock_held() returns + * false even if the CPU did an rcu_read_lock(). The reason for this is + * that RCU ignores CPUs that are in extended quiescent states, so such + * a CPU is effectively never in an RCU read-side critical section + * regardless of what RCU primitives it invokes. This state of affairs + * is required -- RCU would otherwise need to periodically wake up + * dyntick-idle CPUs, which would defeat the whole purpose of dyntick-idle + * mode. */ static inline int srcu_read_lock_held(struct srcu_struct *sp) { if (debug_locks) return lock_is_held(&sp->dep_map); + if (rcu_check_extended_qs()) + return 0; return 1; } @@ -150,7 +155,7 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) { int retval = __srcu_read_lock(sp); - srcu_read_acquire(sp); + rcu_lock_acquire(&(sp)->dep_map); return retval; } @@ -164,7 +169,7 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp) { - srcu_read_release(sp); + rcu_lock_release(&(sp)->dep_map); __srcu_read_unlock(sp, idx); } -- 2.39.5