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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2014-04-29 16:07:28 -0400
committerSteven Rostedt <rostedt@goodmis.org>2014-04-29 16:07:28 -0400
commitf4874261049e3abdd481359d82cafa5068369ebd (patch)
treeee81269a6086634c7ae04c18eba24fb717528590 /kernel/trace
parent8d1b065d47ff1424b1aef7a6aa605b467694c120 (diff)
downloadop-kernel-dev-f4874261049e3abdd481359d82cafa5068369ebd.zip
op-kernel-dev-f4874261049e3abdd481359d82cafa5068369ebd.tar.gz
tracing: Break out of tracing_wait_pipe() before wait_pipe() is called
When reading from trace_pipe, if tracing is off but nothing was read it should block. If something is read and tracing is off, then EOF is returned. If tracing is on and there's nothing to read, it will block. But because the check of whether tracing is off and something was read is done after the block on the pipe, it is hit or miss if the EOF is returned or not leading to inconsistent behavior. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/trace.c18
1 files changed, 9 insertions, 9 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index cb41e98..e058c60 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4237,15 +4237,6 @@ static int tracing_wait_pipe(struct file *filp)
return -EAGAIN;
}
- mutex_unlock(&iter->mutex);
-
- iter->trace->wait_pipe(iter);
-
- mutex_lock(&iter->mutex);
-
- if (signal_pending(current))
- return -EINTR;
-
/*
* We block until we read something and tracing is disabled.
* We still block if tracing is disabled, but we have never
@@ -4257,6 +4248,15 @@ static int tracing_wait_pipe(struct file *filp)
*/
if (!tracing_is_on() && iter->pos)
break;
+
+ mutex_unlock(&iter->mutex);
+
+ iter->trace->wait_pipe(iter);
+
+ mutex_lock(&iter->mutex);
+
+ if (signal_pending(current))
+ return -EINTR;
}
return 1;
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