Re: [PATCH 1/1] sched: CPU remove deadlock fix

Ingo Molnar
2008-12-09T18:27:52Z

* Brian King <brking@linux.vnet.ibm.com> wrote:

> This patch fixes a possible deadlock scenario in the CPU remove path.
> migration_call grabs rq->lock, then wakes up everything on
> rq->migration_queue with the lock held. Then one of the tasks on the
> migration queue ends up calling tg_shares_up which then also tries to
> acquire the same rq->lock.
>
> [c000000058eab2e0] c000000000502078 ._spin_lock_irqsave+0x98/0xf0
> [c000000058eab370] c00000000008011c .tg_shares_up+0x10c/0x20c
> [c000000058eab430] c00000000007867c .walk_tg_tree+0xc4/0xfc
> [c000000058eab4d0] c0000000000840c8 .try_to_wake_up+0xb0/0x3c4
> [c000000058eab590] c0000000000799a0 .__wake_up_common+0x6c/0xe0
> [c000000058eab640] c00000000007ada4 .complete+0x54/0x80
> [c000000058eab6e0] c000000000509fa8 .migration_call+0x5fc/0x6f8
> [c000000058eab7c0] c000000000504074 .notifier_call_chain+0x68/0xe0
> [c000000058eab860] c000000000506568 ._cpu_down+0x2b0/0x3f4
> [c000000058eaba60] c000000000506750 .cpu_down+0xa4/0x108
> [c000000058eabb10] c000000000507e54 .store_online+0x44/0xa8
> [c000000058eabba0] c000000000396260 .sysdev_store+0x3c/0x50
> [c000000058eabc10] c0000000001a39b8 .sysfs_write_file+0x124/0x18c
> [c000000058eabcd0] c00000000013061c .vfs_write+0xd0/0x1bc
> [c000000058eabd70] c0000000001308a4 .sys_write+0x68/0x114
> [c000000058eabe30] c0000000000086b4 syscall_exit+0x0/0x40
>
> Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
> ---
>
> kernel/sched.c | 2 ++
> 1 file changed, 2 insertions(+)

good catch - applied to tip/sched/urgent, thanks Brian!

Ingo