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tracing: Break out of tracing_wait_pipe() before wait_pipe() is called

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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>
This commit is contained in:
Steven Rostedt (Red Hat) 2014-04-29 16:07:28 -04:00 committed by Steven Rostedt
parent 8d1b065d47
commit f487426104
1 changed files with 9 additions and 9 deletions
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18
kernel/trace/trace.c
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@ -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;