From: Martin Wilck <mwilck@xxxxxxxx>
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 <nvme_anatt_timeout>,
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 <mwilck@xxxxxxxx>
Reviewed-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
Reviewed-by: Chao Leng <lengchao@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
----
Changes in v3: Changed the subject line, as suggested by Sagi Grimberg
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
