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>
5.4-rM2-2.2.x-imx-squashed
parent
8a7bfa3d97
commit
e349287276
|
@ -6537,9 +6537,10 @@ static void *fpid_next(struct seq_file *m, void *v, loff_t *pos)
|
|||
struct trace_array *tr = m->private;
|
||||
struct trace_pid_list *pid_list = rcu_dereference_sched(tr->function_pids);
|
||||
|
||||
if (v == FTRACE_NO_PIDS)
|
||||
if (v == FTRACE_NO_PIDS) {
|
||||
(*pos)++;
|
||||
return NULL;
|
||||
|
||||
}
|
||||
return trace_pid_next(pid_list, v, pos);
|
||||
}
|
||||
|
||||
|
|
Loading…
Reference in New Issue