| | Date | Tue, 30 Mar 2010 15:40:55 -0700 | | From | Greg KH <> | | Subject | [021/156] tracing: Fix warning in s_next of trace file ops |
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2.6.33-stable review patch. If anyone has any objections, please let us know.
------------------ From: Lai Jiangshan <laijs@cn.fujitsu.com>
commit ac91d85456372a90af5b85eb6620fd2efb1e431b upstream.
This warning in s_next() can be triggered by lseek(): [<c018b3f7>] ? s_next+0x77/0x80 [<c013e3c1>] warn_slowpath_common+0x81/0xa0 [<c018b3f7>] ? s_next+0x77/0x80 [<c013e3fa>] warn_slowpath_null+0x1a/0x20 [<c018b3f7>] s_next+0x77/0x80 [<c01efa77>] traverse+0x117/0x200 [<c01eff13>] seq_lseek+0xa3/0x120 [<c01efe70>] ? seq_lseek+0x0/0x120 [<c01d7081>] vfs_llseek+0x41/0x50 [<c01d8116>] sys_llseek+0x66/0xa0 [<c0102bd0>] sysenter_do_call+0x12/0x26
The iterator "leftover" variable is zeroed in the opening of the trace file. But lseek can call s_start() which will call s_next() without reseting the "leftover" variable back to zero, which might trigger the WARN_ON_ONCE(iter->leftover) that is in s_next().
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <4B8CE06A.9090207@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- kernel/trace/trace.c | 1 + 1 file changed, 1 insertion(+) --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1628,6 +1628,7 @@ static void *s_start(struct seq_file *m, ftrace_enable_cpu(); + iter->leftover = 0; for (p = iter; p && l < *pos; p = s_next(m, p, &l)) ;
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