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author | KOBAYASHI Yoshitake <yoshitake.kobayashi@toshiba.co.jp> | 2011-07-23 11:57:36 +0900 |
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committer | Steven Rostedt <rostedt@goodmis.org> | 2012-06-07 07:46:55 -0400 |
commit | f1c3c947ac5f2f33ba5b7fe02ce1055fded51130 (patch) | |
tree | 1467fdfc2296cb8237be4a96ceb452088fbe830e /ipc/mq_sysctl.c | |
parent | 1dbc50fbdb1e33fc7b5a89f2811dd8d9e770d17c (diff) |
ipc/mqueue: Add a critical section to avoid a deadlock
(Repost for v3.0-rt1 and changed the distination addreses)
I have tested the following patch on v3.0-rt1 with PREEMPT_RT_FULL.
In POSIX message queue, if a sender process uses SCHED_FIFO and
has a higher priority than a receiver process, the sender will
be stuck at ipc/mqueue.c:452
452 while (ewp->state == STATE_PENDING)
453 cpu_relax();
Description of the problem
(receiver process)
1. receiver changes sender's state to STATE_PENDING (mqueue.c:846)
2. wake up sender process and "switch to sender" (mqueue.c:847)
Note: This context switch only happens in PREEMPT_RT_FULL kernel.
(sender process)
3. sender check the own state in above loop (mqueue.c:452-453)
*. receiver will never wake up and cannot change sender's state to
STATE_READY because sender has higher priority
Signed-off-by: Yoshitake Kobayashi <yoshitake.kobayashi@toshiba.co.jp>
Cc: viro@zeniv.linux.org.uk
Cc: dchinner@redhat.com
Cc: npiggin@kernel.dk
Cc: hch@lst.de
Cc: arnd@arndb.de
Link: http://lkml.kernel.org/r/4E2A38A0.1090601@toshiba.co.jp
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'ipc/mq_sysctl.c')
0 files changed, 0 insertions, 0 deletions