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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2016-01-13 15:48:54 -0500
committerSteven Rostedt <rostedt@goodmis.org>2016-01-14 09:28:19 -0500
commit7717c6be699975f6733d278b13b7c4295d73caf6 (patch)
tree93de22146f1bba873c57d0d98b232c75b0a3727f /kernel/trace
parentafd2ff9b7e1b367172f18ba7f693dfb62bdcb2dc (diff)
downloadlinux-7717c6be699975f6733d278b13b7c4295d73caf6.tar.bz2
tracing: Fix stacktrace skip depth in trace_buffer_unlock_commit_regs()
While cleaning the stacktrace code I unintentially changed the skip depth of trace_buffer_unlock_commit_regs() from 0 to 6. kprobes uses this function, and with skipping 6 call backs, it can easily produce no stack. Here's how I tested it: # echo 'p:ext4_sync_fs ext4_sync_fs ' > /sys/kernel/debug/tracing/kprobe_events # echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable # cat /sys/kernel/debug/trace sync-2394 [005] 502.457060: ext4_sync_fs: (ffffffff81317650) sync-2394 [005] 502.457063: kernel_stack: <stack trace> sync-2394 [005] 502.457086: ext4_sync_fs: (ffffffff81317650) sync-2394 [005] 502.457087: kernel_stack: <stack trace> sync-2394 [005] 502.457091: ext4_sync_fs: (ffffffff81317650) After putting back the skip stack to zero, we have: sync-2270 [000] 748.052693: ext4_sync_fs: (ffffffff81317650) sync-2270 [000] 748.052695: kernel_stack: <stack trace> => iterate_supers (ffffffff8126412e) => sys_sync (ffffffff8129c4b6) => entry_SYSCALL_64_fastpath (ffffffff8181f0b2) sync-2270 [000] 748.053017: ext4_sync_fs: (ffffffff81317650) sync-2270 [000] 748.053019: kernel_stack: <stack trace> => iterate_supers (ffffffff8126412e) => sys_sync (ffffffff8129c4b6) => entry_SYSCALL_64_fastpath (ffffffff8181f0b2) sync-2270 [000] 748.053381: ext4_sync_fs: (ffffffff81317650) sync-2270 [000] 748.053383: kernel_stack: <stack trace> => iterate_supers (ffffffff8126412e) => sys_sync (ffffffff8129c4b6) => entry_SYSCALL_64_fastpath (ffffffff8181f0b2) Cc: stable@vger.kernel.org # v4.4+ Fixes: 73dddbb57bb0 "tracing: Only create stacktrace option when STACKTRACE is configured" Reported-by: Brendan Gregg <brendan.d.gregg@gmail.com> Tested-by: Brendan Gregg <brendan.d.gregg@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/trace.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 87fb9801bd9e..d9293402ee68 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1751,7 +1751,7 @@ void trace_buffer_unlock_commit_regs(struct trace_array *tr,
{
__buffer_unlock_commit(buffer, event);
- ftrace_trace_stack(tr, buffer, flags, 6, pc, regs);
+ ftrace_trace_stack(tr, buffer, flags, 0, pc, regs);
ftrace_trace_userstack(buffer, flags, pc);
}
EXPORT_SYMBOL_GPL(trace_buffer_unlock_commit_regs);