From: Andreas Herrmann This should limit a possible recursion that can lead to a stack overflow like follows: Kernel stack overflow. CPU: 3 Not tainted Process zfcperp0.0.d819 (pid: 13897, task: 000000003e0d8cc8, ksp: 000000003499dbb8) Krnl PSW : 0404000180000000 000000000030f8b2 (get_device+0x12/0x48) Krnl GPRS: 00000000135a1980 000000000030f758 000000003ed6c1e8 0000000000000005 0000000000000000 000000000044a780 000000003dbf7000 0000000034e15800 000000003621c048 070000003499c108 000000003499c1a0 000000003ed6c000 0000000040895000 00000000408ab630 000000003499c0a0 000000003499c0a0 Krnl Code: a7 fb ff e8 a7 19 00 00 b9 02 00 22 e3 e0 f0 98 00 24 a7 84 Call Trace: ([<000000004089edc2>] scsi_request_fn+0x13e/0x650 [scsi_mod]) [<00000000002c5ff4>] blk_run_queue+0xd4/0x1a4 [<000000004089ff8c>] scsi_queue_insert+0x22c/0x2a4 [scsi_mod] [<000000004089779a>] scsi_dispatch_cmd+0x8a/0x3d0 [scsi_mod] [<000000004089f1ec>] scsi_request_fn+0x568/0x650 [scsi_mod] ... [<000000004089f1ec>] scsi_request_fn+0x568/0x650 [scsi_mod] [<00000000002c5ff4>] blk_run_queue+0xd4/0x1a4 [<000000004089ff8c>] scsi_queue_insert+0x22c/0x2a4 [scsi_mod] [<000000004089779a>] scsi_dispatch_cmd+0x8a/0x3d0 [scsi_mod] [<000000004089f1ec>] scsi_request_fn+0x568/0x650 [scsi_mod] [<00000000002c5ff4>] blk_run_queue+0xd4/0x1a4 [<000000004089fa9e>] scsi_run_host_queues+0x196/0x230 [scsi_mod] [<00000000409eba28>] zfcp_erp_thread+0x2638/0x3080 [zfcp] [<0000000000107462>] kernel_thread_starter+0x6/0xc [<000000000010745c>] kernel_thread_starter+0x0/0xc <0>Kernel panic - not syncing: Corrupt kernel stack, can't continue. This stack overflow occurred during tests on s390 using zfcp. Recursion depth for this panic was 19. Usually recursion between blk_run_queue and a request_fn is avoided using QUEUE_FLAG_REENTER. But this does not help if the scsi stack tries to flush the starved_list of a scsi_host. Signed-off-by: Andreas Herrmann Cc: James Bottomley Cc: Jens Axboe Signed-off-by: Andrew Morton --- drivers/scsi/scsi_lib.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff -puN drivers/scsi/scsi_lib.c~scsi-limit-recursion-when-flushing-shost-starved_list drivers/scsi/scsi_lib.c --- a/drivers/scsi/scsi_lib.c~scsi-limit-recursion-when-flushing-shost-starved_list +++ a/drivers/scsi/scsi_lib.c @@ -553,7 +553,15 @@ static void scsi_run_queue(struct reques list_del_init(&sdev->starved_entry); spin_unlock_irqrestore(shost->host_lock, flags); - blk_run_queue(sdev->request_queue); + + if (test_bit(QUEUE_FLAG_REENTER, &q->queue_flags) && + !test_and_set_bit(QUEUE_FLAG_REENTER, + &sdev->request_queue->queue_flags)) { + blk_run_queue(sdev->request_queue); + clear_bit(QUEUE_FLAG_REENTER, + &sdev->request_queue->queue_flags); + } else + blk_run_queue(sdev->request_queue); spin_lock_irqsave(shost->host_lock, flags); if (unlikely(!list_empty(&sdev->starved_entry))) _