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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org From: Martin Wilck We have observed a few crashes run_timer_softirq(), where a broken timer_list struct belonging to an anatt_timer was encountered. The broken structures look like this, and we see actually multiple ones attached to the same timer base: crash> struct timer_list 0xffff92471bcfdc90 struct timer_list { entry = { next = 0xdead000000000122, // LIST_POISON2 pprev = 0x0 }, expires = 4296022933, function = 0xffffffffc06de5e0 , flags = 20 } If such a timer is encountered in run_timer_softirq(), the kernel crashes. The test scenario was an I/O load test with lots of NVMe controllers, some of which were removed and re-added on the storage side. I think this may happen if the rdma recovery_work starts, in this call chain: nvme_rdma_error_recovery_work() /* this stops all sorts of activity for the controller, but not the multipath-related work queue and timer */ nvme_rdma_reconnect_or_remove(ctrl) => kicks reconnect_work work queue: reconnect_work nvme_rdma_reconnect_ctrl_work() nvme_rdma_setup_ctrl() nvme_rdma_configure_admin_queue() nvme_init_identify() nvme_mpath_init() # this sets some fields of the timer_list without taking a lock timer_setup() nvme_read_ana_log() mod_timer() or del_timer_sync() Similar for TCP. The idea for the patch is based on the observation that nvme_rdma_reset_ctrl_work() calls nvme_stop_ctrl()->nvme_mpath_stop(), whereas nvme_rdma_error_recovery_work() stops only the keepalive timer, but not the anatt timer. I admit that the root cause analysis isn't rock solid yet. In particular, I can't explain why we see LIST_POISON2 in the "next" pointer, which would indicate that the timer has been detached before; yet we find it linked to the timer base when the crash occurs. OTOH, the anatt_timer is only touched in nvme_mpath_init() (see above) and nvme_mpath_stop(), so the hypothesis that modifying active timers may cause the issue isn't totally out of sight. I suspect that the LIST_POISON2 may come to pass in multiple steps. If anyone has better ideas, please advise. The issue occurs very sporadically; verifying this by testing will be difficult. Signed-off-by: Martin Wilck ---- Changes in v2: Moved call to nvme_mpath_stop() further down, directly before the call of nvme_rdma_reconnect_or_remove() (Chao Leng) --- drivers/nvme/host/multipath.c | 1 + drivers/nvme/host/rdma.c | 1 + drivers/nvme/host/tcp.c | 1 + 3 files changed, 3 insertions(+) diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c index a1d476e1ac02..c63dd5dfa7ff 100644 --- a/drivers/nvme/host/multipath.c +++ b/drivers/nvme/host/multipath.c @@ -586,6 +586,7 @@ void nvme_mpath_stop(struct nvme_ctrl *ctrl) del_timer_sync(&ctrl->anatt_timer); cancel_work_sync(&ctrl->ana_work); } +EXPORT_SYMBOL_GPL(nvme_mpath_stop); #define SUBSYS_ATTR_RW(_name, _mode, _show, _store) \ struct device_attribute subsys_attr_##_name = \ diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c index be905d4fdb47..fc07a7b0dc1d 100644 --- a/drivers/nvme/host/rdma.c +++ b/drivers/nvme/host/rdma.c @@ -1202,6 +1202,7 @@ static void nvme_rdma_error_recovery_work(struct work_struct *work) return; } + nvme_mpath_stop(&ctrl->ctrl); nvme_rdma_reconnect_or_remove(ctrl); } diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c index a0f00cb8f9f3..46287b4f4d10 100644 --- a/drivers/nvme/host/tcp.c +++ b/drivers/nvme/host/tcp.c @@ -2068,6 +2068,7 @@ static void nvme_tcp_error_recovery_work(struct work_struct *work) return; } + nvme_mpath_stop(ctrl); nvme_tcp_reconnect_or_remove(ctrl); } -- 2.31.1 _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme