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ftrace: fpid_next() should increase position index
[ Upstream commit e4075e8bdf
]
if seq_file .next fuction does not change position index,
read after some lseek can generate unexpected output.
Without patch:
# dd bs=4 skip=1 if=/sys/kernel/tracing/set_ftrace_pid
dd: /sys/kernel/tracing/set_ftrace_pid: cannot skip to specified offset
id
no pid
2+1 records in
2+1 records out
10 bytes copied, 0.000213285 s, 46.9 kB/s
Notice the "id" followed by "no pid".
With the patch:
# dd bs=4 skip=1 if=/sys/kernel/tracing/set_ftrace_pid
dd: /sys/kernel/tracing/set_ftrace_pid: cannot skip to specified offset
id
0+1 records in
0+1 records out
3 bytes copied, 0.000202112 s, 14.8 kB/s
Notice that it only prints "id" and not the "no pid" afterward.
Link: http://lkml.kernel.org/r/4f87c6ad-f114-30bb-8506-c32274ce2992@virtuozzo.com
https://bugzilla.kernel.org/show_bug.cgi?id=206283
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
parent
ae2f1cd6a3
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@ -6525,9 +6525,10 @@ static void *fpid_next(struct seq_file *m, void *v, loff_t *pos)
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struct trace_array *tr = m->private;
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struct trace_pid_list *pid_list = rcu_dereference_sched(tr->function_pids);
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if (v == FTRACE_NO_PIDS)
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if (v == FTRACE_NO_PIDS) {
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(*pos)++;
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return NULL;
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}
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return trace_pid_next(pid_list, v, pos);
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}
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