locking/mutexes: don't spin on owner when wait list is not NULL.
I build a script to create several process for ioctl loop calling,
the ioctl will calling the kernel function just like:
xx_ioctl {
...
rtnl_lock();
function();
rtnl_unlock();
...
}
The function may sleep several ms, but will not halt, at the same time
another user service may calling ifconfig to change the state of the
ethernet, and after several hours, the hung task thread report this problem:
========================================================================
149738.039038] INFO: task ifconfig:11890 blocked for more than 120 seconds.
[149738.040597] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[149738.042280] ifconfig D ffff88061ec13680 0 11890 11573 0x00000080
[149738.042284] ffff88052449bd40 0000000000000082 ffff88053a33f300 ffff88052449bfd8
[149738.042286] ffff88052449bfd8 ffff88052449bfd8 ffff88053a33f300 ffffffff819e6240
[149738.042288] ffffffff819e6244 ffff88053a33f300 00000000ffffffff ffffffff819e6248
[149738.042290] Call Trace:
[149738.042300] [<ffffffff8160d219>] schedule_preempt_disabled+0x29/0x70
[149738.042303] [<ffffffff8160af65>] __mutex_lock_slowpath+0xc5/0x1c0
[149738.042305] [<ffffffff8160a3cf>] mutex_lock+0x1f/0x2f
[149738.042309] [<ffffffff8150d945>] rtnl_lock+0x15/0x20
[149738.042311] [<ffffffff81514e3a>] dev_ioctl+0xda/0x590
[149738.042314] [<ffffffff816121cc>] ? __do_page_fault+0x21c/0x560
[149738.042318] [<ffffffff814e42c5>] sock_do_ioctl+0x45/0x50
[149738.042320] [<ffffffff814e49d0>] sock_ioctl+0x1f0/0x2c0
[149738.042324] [<ffffffff811dc9b5>] do_vfs_ioctl+0x2e5/0x4c0
[149738.042327] [<ffffffff811e6a00>] ? fget_light+0xa0/0xd0
================================ cut here ================================
I got the vmcore and found that the ifconfig is already in the wait_list of the
rtnl_lock for 120 second, but my process could get and release the rtnl_lock
normally several times in one second, so it means that my process jump the
queue and the ifconfig couldn't get the rtnl all the time, I check the mutex lock
slow path and found that the mutex may spin on owner ignore whether the wait list
is empty, it will cause the task in the wait list always be cut in line, so add
test for wait list in the mutex_can_spin_on_owner and avoid this problem.
Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
1 file changed
