From 9fa73472ddbcd3da87d35a7f4566eaaf345f798e Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Mon, 6 Feb 2012 08:57:29 +0100 Subject: [PATCH] block: fix ioc locking warning Meelis reported a warning: WARNING: at kernel/timer.c:1122 run_timer_softirq+0x199/0x1ec() Hardware name: 939Dual-SATA2 timer: cfq_idle_slice_timer+0x0/0xaa preempt leak: 00000102 -> 00000103 Modules linked in: sr_mod cdrom videodev media drm_kms_helper ohci_hcd ehci_hcd v4l2_compat_ioctl32 usbcore i2c_ali15x3 snd_seq drm snd_timer snd_seq Pid: 0, comm: swapper Not tainted 3.3.0-rc2-00110-gd125666 #176 Call Trace: [] warn_slowpath_common+0x7e/0x96 [] ? cfq_slice_expired+0x1d/0x1d [] warn_slowpath_fmt+0x41/0x43 [] ? cfq_idle_slice_timer+0xa1/0xaa [] ? cfq_slice_expired+0x1d/0x1d [] run_timer_softirq+0x199/0x1ec [] ? timekeeping_get_ns+0x12/0x31 [] ? apic_write+0x11/0x13 [] __do_softirq+0x74/0xfa [] call_softirq+0x1a/0x30 [] do_softirq+0x31/0x68 [] irq_exit+0x3d/0xa3 [] smp_apic_timer_interrupt+0x6b/0x77 [] apic_timer_interrupt+0x69/0x70 [] ? sched_clock_cpu+0x73/0x7d [] ? sched_clock_cpu+0x73/0x7d [] ? default_idle+0x1e/0x32 [] ? default_idle+0x18/0x32 [] cpu_idle+0x87/0xd1 [] rest_init+0x85/0x89 [] start_kernel+0x2eb/0x2f8 [] x86_64_start_reservations+0x7e/0x82 [] x86_64_start_kernel+0xf0/0xf7 this_q == locked_q is possible. There are two problems here: 1. In UP case, there is preemption counter issue as spin_trylock always successes. 2. In SMP case, the loop breaks too earlier. Signed-off-by: Shaohua Li Reported-by: Meelis Roos Reported-by: Knut Petersen Tested-by: Knut Petersen Signed-off-by: Jens Axboe --- block/blk-ioc.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/block/blk-ioc.c b/block/blk-ioc.c index 27a06e00eaec..7490b6da2453 100644 --- a/block/blk-ioc.c +++ b/block/blk-ioc.c @@ -204,7 +204,9 @@ void put_io_context(struct io_context *ioc, struct request_queue *locked_q) spin_unlock(last_q->queue_lock); last_q = NULL; - if (!spin_trylock(this_q->queue_lock)) + /* spin_trylock() always successes in UP case */ + if (this_q != locked_q && + !spin_trylock(this_q->queue_lock)) break; last_q = this_q; continue; -- 2.30.2