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authorFrederic Weisbecker <fweisbec@gmail.com>2010-02-02 17:34:40 -0500
committerFrederic Weisbecker <fweisbec@gmail.com>2010-03-10 08:26:07 -0500
commitdb2c4c7791cd04512093d05afc693c3511a65fd7 (patch)
tree11ad51f5ec2010e32edde2dea5696f90822435f4 /kernel
parent65f2ed2b2fa6034ef9890b60c8fd39fbe76b9d37 (diff)
lockdep: Move lock events under lockdep recursion protection
There are rcu locked read side areas in the path where we submit a trace event. And these rcu_read_(un)lock() trigger lock events, which create recursive events. One pair in do_perf_sw_event: __lock_acquire | |--96.11%-- lock_acquire | | | |--27.21%-- do_perf_sw_event | | perf_tp_event | | | | | |--49.62%-- ftrace_profile_lock_release | | | lock_release | | | | | | | |--33.85%-- _raw_spin_unlock Another pair in perf_output_begin/end: __lock_acquire |--23.40%-- perf_output_begin | | __perf_event_overflow | | perf_swevent_overflow | | perf_swevent_add | | perf_swevent_ctx_event | | do_perf_sw_event | | perf_tp_event | | | | | |--55.37%-- ftrace_profile_lock_acquire | | | lock_acquire | | | | | | | |--37.31%-- _raw_spin_lock The problem is not that much the trace recursion itself, as we have a recursion protection already (though it's always wasteful to recurse). But the trace events are outside the lockdep recursion protection, then each lockdep event triggers a lock trace, which will trigger two other lockdep events. Here the recursive lock trace event won't be taken because of the trace recursion, so the recursion stops there but lockdep will still analyse these new events: To sum up, for each lockdep events we have: lock_*() | trace lock_acquire | ----- rcu_read_lock() | | | lock_acquire() | | | trace_lock_acquire() (stopped) | | | lockdep analyze | ----- rcu_read_unlock() | lock_release | trace_lock_release() (stopped) | lockdep analyze And you can repeat the above two times as we have two rcu read side sections when we submit an event. This is fixed in this patch by moving the lock trace event under the lockdep recursion protection. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Masami Hiramatsu <mhiramat@redhat.com> Cc: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/lockdep.c9
1 files changed, 3 insertions, 6 deletions
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 0c30d0455de1..65b5f5b7c298 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -3211,8 +3211,6 @@ void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3211{ 3211{
3212 unsigned long flags; 3212 unsigned long flags;
3213 3213
3214 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
3215
3216 if (unlikely(current->lockdep_recursion)) 3214 if (unlikely(current->lockdep_recursion))
3217 return; 3215 return;
3218 3216
@@ -3220,6 +3218,7 @@ void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3220 check_flags(flags); 3218 check_flags(flags);
3221 3219
3222 current->lockdep_recursion = 1; 3220 current->lockdep_recursion = 1;
3221 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
3223 __lock_acquire(lock, subclass, trylock, read, check, 3222 __lock_acquire(lock, subclass, trylock, read, check,
3224 irqs_disabled_flags(flags), nest_lock, ip, 0); 3223 irqs_disabled_flags(flags), nest_lock, ip, 0);
3225 current->lockdep_recursion = 0; 3224 current->lockdep_recursion = 0;
@@ -3232,14 +3231,13 @@ void lock_release(struct lockdep_map *lock, int nested,
3232{ 3231{
3233 unsigned long flags; 3232 unsigned long flags;
3234 3233
3235 trace_lock_release(lock, nested, ip);
3236
3237 if (unlikely(current->lockdep_recursion)) 3234 if (unlikely(current->lockdep_recursion))
3238 return; 3235 return;
3239 3236
3240 raw_local_irq_save(flags); 3237 raw_local_irq_save(flags);
3241 check_flags(flags); 3238 check_flags(flags);
3242 current->lockdep_recursion = 1; 3239 current->lockdep_recursion = 1;
3240 trace_lock_release(lock, nested, ip);
3243 __lock_release(lock, nested, ip); 3241 __lock_release(lock, nested, ip);
3244 current->lockdep_recursion = 0; 3242 current->lockdep_recursion = 0;
3245 raw_local_irq_restore(flags); 3243 raw_local_irq_restore(flags);
@@ -3413,8 +3411,6 @@ void lock_contended(struct lockdep_map *lock, unsigned long ip)
3413{ 3411{
3414 unsigned long flags; 3412 unsigned long flags;
3415 3413
3416 trace_lock_contended(lock, ip);
3417
3418 if (unlikely(!lock_stat)) 3414 if (unlikely(!lock_stat))
3419 return; 3415 return;
3420 3416
@@ -3424,6 +3420,7 @@ void lock_contended(struct lockdep_map *lock, unsigned long ip)
3424 raw_local_irq_save(flags); 3420 raw_local_irq_save(flags);
3425 check_flags(flags); 3421 check_flags(flags);
3426 current->lockdep_recursion = 1; 3422 current->lockdep_recursion = 1;
3423 trace_lock_contended(lock, ip);
3427 __lock_contended(lock, ip); 3424 __lock_contended(lock, ip);
3428 current->lockdep_recursion = 0; 3425 current->lockdep_recursion = 0;
3429 raw_local_irq_restore(flags); 3426 raw_local_irq_restore(flags);