Commit ac91d854 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Steven Rostedt
Browse files

tracing: Fix warning in s_next of trace file ops

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: default avatarLai Jiangshan <>
LKML-Reference: <>
Signed-off-by: default avatarSteven Rostedt <>
parent 3a5b27bf
......@@ -1703,6 +1703,7 @@ static void *s_start(struct seq_file *m, loff_t *pos)
iter->leftover = 0;
for (p = iter; p && l < *pos; p = s_next(m, p, &l))
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