From 52494535103986dbbf689b44d8c2c7efe2132b16 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 14 Nov 2012 16:26:40 -0800 Subject: rcu: Reduce rcutorture tracing Currently, rcutorture traces every read-side access. This can be problematic because even a two-minute rcutorture run on a two-CPU system can generate 28,853,363 reads. Normally, only a failing read is of interest, so this commit traces adjusts rcutorture's tracing to only trace failing reads. The resulting event tracing records the time and the ->completed value captured at the beginning of the RCU read-side critical section, allowing correlation with other event-tracing messages. Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett [ paulmck: Add fix to build problem located by Randy Dunlap based on diagnosis by Steven Rostedt. ] --- include/linux/rcupdate.h | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) (limited to 'include/linux') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 275aa3f1062d..7f89cea596e1 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -53,7 +53,10 @@ extern int rcutorture_runnable; /* for sysctl */ extern void rcutorture_record_test_transition(void); extern void rcutorture_record_progress(unsigned long vernum); extern void do_trace_rcu_torture_read(char *rcutorturename, - struct rcu_head *rhp); + struct rcu_head *rhp, + unsigned long secs, + unsigned long c_old, + unsigned long c); #else static inline void rcutorture_record_test_transition(void) { @@ -63,9 +66,13 @@ static inline void rcutorture_record_progress(unsigned long vernum) } #ifdef CONFIG_RCU_TRACE extern void do_trace_rcu_torture_read(char *rcutorturename, - struct rcu_head *rhp); + struct rcu_head *rhp, + unsigned long secs, + unsigned long c_old, + unsigned long c); #else -#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0) +#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ + do { } while (0) #endif #endif -- cgit v1.2.3 From 90f45e4e729a7ffaa3ed2423834aad612870b427 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 10 Jan 2013 05:24:49 -0800 Subject: rcu: Remove obsolete Kconfig option from comment Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 275aa3f1062d..7e12dbaa1457 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -749,7 +749,7 @@ static inline void rcu_preempt_sleep_check(void) * preemptible RCU implementations (TREE_PREEMPT_RCU and TINY_PREEMPT_RCU) * in CONFIG_PREEMPT kernel builds, RCU read-side critical sections may * be preempted, but explicit blocking is illegal. Finally, in preemptible - * RCU implementations in real-time (CONFIG_PREEMPT_RT) kernel builds, + * RCU implementations in real-time (with -rt patchset) kernel builds, * RCU read-side critical sections may be preempted and they may also * block, but only when acquiring spinlocks that are subject to priority * inheritance. -- cgit v1.2.3 From 3bc97a782cc8c112f64a25143452b06206364cc8 Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Thu, 29 Nov 2012 16:46:05 +0800 Subject: srcu: Remove checks preventing offline CPUs from calling srcu_read_lock() SRCU has its own statemachine and no longer relies on normal RCU. Its read-side critical section can now be used by an offline CPU, so this commit removes the check and the comments, reverting the SRCU portion of c0d6d01b (rcu: Check for illegal use of RCU from offlined CPUs). It also makes the code match the comments in whatisRCU.txt: g. Do you need read-side critical sections that are respected even though they are in the middle of the idle loop, during user-mode execution, or on an offlined CPU? If so, SRCU is the only choice that will work for you. [ paulmck: There is at least one remaining issue, namely use of lockdep with tracing enabled. ] Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney --- include/linux/srcu.h | 5 ----- 1 file changed, 5 deletions(-) (limited to 'include/linux') diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 6eb691b08358..ae3ee39eb699 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -163,9 +163,6 @@ void srcu_barrier(struct srcu_struct *sp); * power mode. This way we can notice an extended quiescent state to * other CPUs that started a grace period. Otherwise we would delay any * grace period as long as we run in the idle task. - * - * Similarly, we avoid claiming an SRCU read lock held if the current - * CPU is offline. */ static inline int srcu_read_lock_held(struct srcu_struct *sp) { @@ -173,8 +170,6 @@ static inline int srcu_read_lock_held(struct srcu_struct *sp) return 1; if (rcu_is_cpu_idle()) return 0; - if (!rcu_lockdep_current_cpu_online()) - return 0; return lock_is_held(&sp->dep_map); } -- cgit v1.2.3 From 511a0868bed6694512348fc177cdfaf3fd97d0bb Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Thu, 29 Nov 2012 16:46:06 +0800 Subject: srcu: Remove checks preventing idle CPUs from calling srcu_read_lock() SRCU has its own statemachine and no longer relies on normal RCU. Its read-side critical section can now be used by an offline CPU, so this commit removes the check and the comments, reverting the SRCU portion of ff195cb6 (rcu: Warn when srcu_read_lock() is used in an extended quiescent state). It also makes the codes match the comments in whatisRCU.txt: g. Do you need read-side critical sections that are respected even though they are in the middle of the idle loop, during user-mode execution, or on an offlined CPU? If so, SRCU is the only choice that will work for you. [ paulmck: There is at least one remaining issue, namely use of lockdep with tracing enabled. ] Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney --- include/linux/srcu.h | 21 +++------------------ 1 file changed, 3 insertions(+), 18 deletions(-) (limited to 'include/linux') diff --git a/include/linux/srcu.h b/include/linux/srcu.h index ae3ee39eb699..04f4121a23ae 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -151,25 +151,14 @@ void srcu_barrier(struct srcu_struct *sp); * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot * and while lockdep is disabled. * - * Note that if the CPU is in the idle loop from an RCU point of view - * (ie: that we are in the section between rcu_idle_enter() and - * rcu_idle_exit()) then srcu_read_lock_held() returns false even if - * the CPU did an srcu_read_lock(). The reason for this is that RCU - * ignores CPUs that are in such a section, considering these as in - * extended quiescent state, 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 --- we need to keep an - * RCU-free window in idle where the CPU may possibly enter into low - * power mode. This way we can notice an extended quiescent state to - * other CPUs that started a grace period. Otherwise we would delay any - * grace period as long as we run in the idle task. + * Note that SRCU is based on its own statemachine and it doesn't + * relies on normal RCU, it can be called from the CPU which + * is in the idle loop from an RCU point of view or offline. */ static inline int srcu_read_lock_held(struct srcu_struct *sp) { if (!debug_lockdep_rcu_enabled()) return 1; - if (rcu_is_cpu_idle()) - return 0; return lock_is_held(&sp->dep_map); } @@ -231,8 +220,6 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) int retval = __srcu_read_lock(sp); rcu_lock_acquire(&(sp)->dep_map); - rcu_lockdep_assert(!rcu_is_cpu_idle(), - "srcu_read_lock() used illegally while idle"); return retval; } @@ -246,8 +233,6 @@ 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) { - rcu_lockdep_assert(!rcu_is_cpu_idle(), - "srcu_read_unlock() used illegally while idle"); rcu_lock_release(&(sp)->dep_map); __srcu_read_unlock(sp, idx); } -- cgit v1.2.3