From f3b9aae16219aaeca2dd5a9ca69f7a10faa063df Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sun, 19 Apr 2009 23:39:33 +0200 Subject: [PATCH] tracing/ring-buffer: Add unlock recursion protection on discard The pair of helpers trace_recursive_lock() and trace_recursive_unlock() have been introduced recently to provide generic tracing recursion protection. They are used in a symetric way: - trace_recursive_lock() on buffer reserve - trace_recursive_unlock() on buffer commit However sometimes, we don't commit but discard on entry to the buffer, ie: in case of filter checking. Then we must also unlock the recursion protection on discard time, otherwise the tracing gets definitely deactivated and a warning is raised spuriously, such as: 111.119821] ------------[ cut here ]------------ [ 111.119829] WARNING: at kernel/trace/ring_buffer.c:1498 ring_buffer_lock_reserve+0x1b7/0x1d0() [ 111.119835] Hardware name: AMILO Li 2727 [ 111.119839] Modules linked in: [ 111.119846] Pid: 5731, comm: Xorg Tainted: G W 2.6.30-rc1 #69 [ 111.119851] Call Trace: [ 111.119863] [] warn_slowpath+0xd8/0x130 [ 111.119873] [] ? __lock_acquire+0x19f/0x1ae0 [ 111.119882] [] ? __lock_acquire+0x19f/0x1ae0 [ 111.119891] [] ? native_sched_clock+0x20/0x70 [ 111.119899] [] ? put_lock_stats+0xe/0x30 [ 111.119906] [] ? lock_release_holdtime+0xa8/0x150 [ 111.119913] [] ring_buffer_lock_reserve+0x1b7/0x1d0 [ 111.119921] [] trace_buffer_lock_reserve+0x30/0x70 [ 111.119930] [] trace_current_buffer_lock_reserve+0x20/0x30 [ 111.119939] [] ftrace_raw_event_sched_switch+0x58/0x100 [ 111.119948] [] __schedule+0x3a7/0x4cd [ 111.119957] [] ? ftrace_call+0x5/0x2b [ 111.119964] [] ? ftrace_call+0x5/0x2b [ 111.119971] [] schedule+0x18/0x40 [ 111.119977] [] preempt_schedule+0x39/0x60 [ 111.119985] [] _read_unlock+0x53/0x60 [ 111.119993] [] sock_def_readable+0x72/0x80 [ 111.120002] [] unix_stream_sendmsg+0x24d/0x3d0 [ 111.120011] [] sock_aio_write+0x143/0x160 [ 111.120019] [] ? ftrace_call+0x5/0x2b [ 111.120026] [] ? sock_aio_write+0x0/0x160 [ 111.120033] [] ? sock_aio_write+0x0/0x160 [ 111.120042] [] do_sync_readv_writev+0xf3/0x140 [ 111.120049] [] ? ftrace_call+0x5/0x2b [ 111.120057] [] ? autoremove_wake_function+0x0/0x40 [ 111.120067] [] ? cap_file_permission+0x9/0x10 [ 111.120074] [] ? security_file_permission+0x16/0x20 [ 111.120082] [] do_readv_writev+0xd4/0x1f0 [ 111.120089] [] ? ftrace_call+0x5/0x2b [ 111.120097] [] ? ftrace_call+0x5/0x2b [ 111.120105] [] vfs_writev+0x48/0x70 [ 111.120111] [] sys_writev+0x55/0xc0 [ 111.120119] [] system_call_fastpath+0x16/0x1b [ 111.120125] ---[ end trace 15605f4e98d5ccb5 ]--- [ Impact: fix spurious warning triggering tracing shutdown ] Signed-off-by: Frederic Weisbecker --- kernel/trace/ring_buffer.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index bffde63..e145969 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1642,6 +1642,14 @@ int ring_buffer_unlock_commit(struct ring_buffer *buffer, } EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit); +static inline void rb_event_discard(struct ring_buffer_event *event) +{ + event->type = RINGBUF_TYPE_PADDING; + /* time delta must be non zero */ + if (!event->time_delta) + event->time_delta = 1; +} + /** * ring_buffer_event_discard - discard any event in the ring buffer * @event: the event to discard @@ -1656,10 +1664,8 @@ EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit); */ void ring_buffer_event_discard(struct ring_buffer_event *event) { - event->type = RINGBUF_TYPE_PADDING; - /* time delta must be non zero */ - if (!event->time_delta) - event->time_delta = 1; + rb_event_discard(event); + trace_recursive_unlock(); } EXPORT_SYMBOL_GPL(ring_buffer_event_discard); @@ -1690,7 +1696,7 @@ void ring_buffer_discard_commit(struct ring_buffer *buffer, int cpu; /* The event is discarded regardless */ - ring_buffer_event_discard(event); + rb_event_discard(event); /* * This must only be called if the event has not been @@ -1735,6 +1741,8 @@ void ring_buffer_discard_commit(struct ring_buffer *buffer, if (rb_is_commit(cpu_buffer, event)) rb_set_commit_to_write(cpu_buffer); + trace_recursive_unlock(); + /* * Only the last preempt count needs to restore preemption. */ -- 2.7.4