diff options
author | Vasiliy Kulikov | 2011-06-27 16:18:11 -0700 |
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committer | Linus Torvalds | 2011-06-27 18:00:13 -0700 |
commit | 26c4caea9d697043cc5a458b96411b86d7f6babd (patch) | |
tree | cf4de2553fbfcafc41eb4f84bc9ee1eb69adf725 /drivers/block/drbd | |
parent | 08142579b6ca35883c1ed066a2681de6f6917062 (diff) |
taskstats: don't allow duplicate entries in listener mode
Currently a single process may register exit handlers unlimited times.
It may lead to a bloated listeners chain and very slow process
terminations.
Eg after 10KK sent TASKSTATS_CMD_ATTR_REGISTER_CPUMASKs ~300 Mb of
kernel memory is stolen for the handlers chain and "time id" shows 2-7
seconds instead of normal 0.003. It makes it possible to exhaust all
kernel memory and to eat much of CPU time by triggerring numerous exits
on a single CPU.
The patch limits the number of times a single process may register
itself on a single CPU to one.
One little issue is kept unfixed - as taskstats_exit() is called before
exit_files() in do_exit(), the orphaned listener entry (if it was not
explicitly deregistered) is kept until the next someone's exit() and
implicit deregistration in send_cpu_listeners(). So, if a process
registered itself as a listener exits and the next spawned process gets
the same pid, it would inherit taskstats attributes.
Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/block/drbd')
0 files changed, 0 insertions, 0 deletions