Vasily Averin ddb005d906 ftrace: fpid_next() should increase position index
[ Upstream commit e4075e8bdffd93a9b6d6e1d52fabedceeca5a91b ]

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>
2020-02-24 08:34:52 +01:00
..
2019-12-13 08:51:11 +01:00
2019-05-31 06:46:17 -07:00
2019-12-01 09:17:17 +01:00
2018-04-27 14:34:51 +02:00
2019-12-01 09:17:38 +01:00
2019-01-13 09:51:06 +01:00
2018-07-03 09:20:44 +02:00
2020-01-09 10:18:59 +01:00
2018-06-07 16:56:28 -04:00