Re: [PATCH 0/5]stop normal completion path entering a timeout req
From: jianchao.wang <hidden>
Date: 2018-06-21 08:22:21
Also in:
linux-scsi, lkml
Subsystem:
scsi subsystem, the rest · Maintainers:
"James E.J. Bottomley", "Martin K. Petersen", Linus Torvalds
Hi Christoph Thanks for your kindly response. On 06/21/2018 04:19 PM, Christoph Hellwig wrote:
On Thu, Jun 21, 2018 at 09:43:26AM +0800, jianchao.wang wrote:quoted
So we have to preserve the ability of block layer that it could prevent IO completion path from entering a timeout request. With scsi-debug module, I tried to simulate a scenario where timeout and IO completion path could occur concurrently, the system ran into crash easily.Trace, please. With the latest kernel. I'm not saying that there is nothing to fix, but the mode of never completing once timeout requests as currently done is SCSI is clearly broken.
I didn't find the existing method to simulate this. So I modified the scsi-debug as following patch as install it as following: modprobe scsi-debug delay=-1 ndelay=-1 Both 4.17-rc1 and 4.18-rc1 with this patch set could survive from the test.
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 24d7496..f278e6c 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c@@ -4323,6 +4323,8 @@ static void setup_inject(struct sdebug_queue *sqp, sqcp->inj_host_busy = !!(SDEBUG_OPT_HOST_BUSY & sdebug_opts); } +static atomic_t g_abort_counter; + /* Complete the processing of the thread that queued a SCSI command to this * driver. It either completes the command by calling cmnd_done() or * schedules a hr timer or work queue then returns 0. Returns
@@ -4459,6 +4461,11 @@ static int schedule_resp(struct scsi_cmnd *cmnd, struct sdebug_dev_info *devip, sd_dp->issuing_cpu = raw_smp_processor_id(); sd_dp->defer_t = SDEB_DEFER_WQ; schedule_work(&sd_dp->ew.work); + atomic_inc(&g_abort_counter); + if (atomic_read(&g_abort_counter)%2000 == 0) { + blk_abort_request(cmnd->request); + trace_printk("abort request tag %d\n", cmnd->request->tag); + } } if (unlikely((SDEBUG_OPT_Q_NOISE & sdebug_opts) && (scsi_result == device_qfull_result)))
@@ -5844,6 +5851,7 @@ static int sdebug_driver_probe(struct device *dev) struct Scsi_Host *hpnt; int hprot; + atomic_set(&g_abort_counter, 0); sdbg_host = to_sdebug_host(dev); sdebug_driver_template.can_queue = sdebug_max_queue;