[PATCH 2/2] tracing/ring-buffer: unlock recursion protection on discard
From: Frederic Weisbecker
Date: Sun Apr 19 2009 - 18:08:42 EST
The pair of helpers trace_recursive_lock() trace_recursive_unlock()
have been introduced recently to provide a 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 en 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 definetly 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] [<ffffffff8025ce68>] warn_slowpath+0xd8/0x130
[ 111.119873] [<ffffffff8028a30f>] ? __lock_acquire+0x19f/0x1ae0
[ 111.119882] [<ffffffff8028a30f>] ? __lock_acquire+0x19f/0x1ae0
[ 111.119891] [<ffffffff802199b0>] ? native_sched_clock+0x20/0x70
[ 111.119899] [<ffffffff80286dee>] ? put_lock_stats+0xe/0x30
[ 111.119906] [<ffffffff80286eb8>] ? lock_release_holdtime+0xa8/0x150
[ 111.119913] [<ffffffff802c8ae7>] ring_buffer_lock_reserve+0x1b7/0x1d0
[ 111.119921] [<ffffffff802cd110>] trace_buffer_lock_reserve+0x30/0x70
[ 111.119930] [<ffffffff802ce000>] trace_current_buffer_lock_reserve+0x20/0x30
[ 111.119939] [<ffffffff802474e8>] ftrace_raw_event_sched_switch+0x58/0x100
[ 111.119948] [<ffffffff808103b7>] __schedule+0x3a7/0x4cd
[ 111.119957] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b
[ 111.119964] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b
[ 111.119971] [<ffffffff80810c08>] schedule+0x18/0x40
[ 111.119977] [<ffffffff80810e09>] preempt_schedule+0x39/0x60
[ 111.119985] [<ffffffff80813bd3>] _read_unlock+0x53/0x60
[ 111.119993] [<ffffffff807259d2>] sock_def_readable+0x72/0x80
[ 111.120002] [<ffffffff807ad5ed>] unix_stream_sendmsg+0x24d/0x3d0
[ 111.120011] [<ffffffff807219a3>] sock_aio_write+0x143/0x160
[ 111.120019] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b
[ 111.120026] [<ffffffff80721860>] ? sock_aio_write+0x0/0x160
[ 111.120033] [<ffffffff80721860>] ? sock_aio_write+0x0/0x160
[ 111.120042] [<ffffffff8031c283>] do_sync_readv_writev+0xf3/0x140
[ 111.120049] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b
[ 111.120057] [<ffffffff80276ff0>] ? autoremove_wake_function+0x0/0x40
[ 111.120067] [<ffffffff8045d489>] ? cap_file_permission+0x9/0x10
[ 111.120074] [<ffffffff8045c1e6>] ? security_file_permission+0x16/0x20
[ 111.120082] [<ffffffff8031cab4>] do_readv_writev+0xd4/0x1f0
[ 111.120089] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b
[ 111.120097] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b
[ 111.120105] [<ffffffff8031cc18>] vfs_writev+0x48/0x70
[ 111.120111] [<ffffffff8031cd65>] sys_writev+0x55/0xc0
[ 111.120119] [<ffffffff80211e32>] system_call_fastpath+0x16/0x1b
[ 111.120125] ---[ end trace 15605f4e98d5ccb5 ]---
[ Impact: fix spurious warning/tracing shutdown ]
Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
---
kernel/trace/ring_buffer.c | 18 +++++++++++++-----
1 files 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.
*/
--
1.6.2.3
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