Removing a SCSI target via scsi_remove_target() suspected to be racy. When a
sibling get's removed from the list it can occassionly happen that one CPU is
stuck endlessly looping around this code block
list_for_each_entry(starget, &shost->__targets, siblings) {
if (starget->state == STARGET_DEL)
continue;
Resulting in the following hard lockup.
Kernel panic - not syncing: Watchdog detected hard LOCKUP on cpu 0
[...]
Call Trace:
[<ffffffff8100471d>] dump_trace+0x7d/0x2d0
[<ffffffff81004a04>] show_stack_log_lvl+0x94/0x170
[<ffffffff81005cc1>] show_stack+0x21/0x50
[<ffffffff8151aa75>] dump_stack+0x41/0x51
[<ffffffff8151545a>] panic+0xc8/0x1d7
[<ffffffff810fbdda>] watchdog_overflow_callback+0xba/0xc0
[<ffffffff811336c8>] __perf_event_overflow+0x88/0x240
[<ffffffff8101e3aa>] intel_pmu_handle_irq+0x1fa/0x3e0
[<ffffffff81522836>] perf_event_nmi_handler+0x26/0x40
[<ffffffff81521fcd>] nmi_handle.isra.2+0x8d/0x180
[<ffffffff815221e6>] do_nmi+0x126/0x3c0
[<ffffffff8152159b>] end_repeat_nmi+0x1a/0x1e
[<ffffffffa00212e8>] scsi_remove_target+0x68/0x240 [scsi_mod]
[<ffffffff81072742>] process_one_work+0x172/0x420
[<ffffffff810733ba>] worker_thread+0x11a/0x3c0
[<ffffffff81079d34>] kthread+0xb4/0xc0
[<ffffffff81528cd8>] ret_from_fork+0x58/0x90
This series attacks the issue by 1) decoupling the __targets and __devices
lists of struct Scsi_Host from the host_lock spinlock by introducing spinlocks
for each list and 2) de-coupling the list traversals needed for detecting
targets/devices to be removed from the actual removal by moving list entries to
be deleted to a second list and perform the deletion there.
The whole series survived a nearly 48h test loop of:
while [ $not_done ]; do
umount $mountpoint;
rmmod $module;
modprobe $module;
mount $mountpoint;
done
This is a follow up of the patch proposed here:
http://marc.info/?l=linux-scsi&m=144377409311774&w=2
incorporating Christoph's comment
Johannes Thumshirn (3):
SCSI: Introduce device_lock and target_lock in Scsi_Host
SCSI: Rework list handling in scsi_target_remove
SCSI: Rework list handling in __scsi_target_remove
drivers/scsi/53c700.c | 3 +++
drivers/scsi/hosts.c | 2 ++
drivers/scsi/scsi.c | 8 ++++----
drivers/scsi/scsi_scan.c | 10 +++++-----
drivers/scsi/scsi_sysfs.c | 43 +++++++++++++++++++++----------------------
include/scsi/scsi_host.h | 2 ++
6 files changed, 37 insertions(+), 31 deletions(-)
--
1.8.5.6
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