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authorBrian King <brking@linux.vnet.ibm.com>2008-12-09 08:47:00 -0600
committerIngo Molnar <mingo@elte.hu>2008-12-09 19:27:03 +0100
commit9a2bd244e18ffbb96c8b783210fda4eded7c7e6f (patch)
tree19ac3da79ea2c7245549cf69e8207a23f635d04e
parent43714539eab42b2fa3653ea7bd667b36c2291b11 (diff)
sched: CPU remove deadlock fix
Impact: fix possible deadlock in CPU hot-remove path 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> Acked-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/sched.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index b7480fb5c3dc..e4bb1dd7b308 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6587,7 +6587,9 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
req = list_entry(rq->migration_queue.next,
struct migration_req, list);
list_del_init(&req->list);
+ spin_unlock_irq(&rq->lock);
complete(&req->done);
+ spin_lock_irq(&rq->lock);
}
spin_unlock_irq(&rq->lock);
break;