From de1ff848c74fcc5b172323c1d5fac88dc1ab0281 Mon Sep 17 00:00:00 2001 From: Chris Leech Date: Mon, 27 Feb 2017 16:58:36 -0800 Subject: scsi: libiscsi: add lock around task lists to fix list corruption regression commit 6f8830f5bbab16e54f261de187f3df4644a5b977 upstream. There's a rather long standing regression from the commit "libiscsi: Reduce locking contention in fast path" Depending on iSCSI target behavior, it's possible to hit the case in iscsi_complete_task where the task is still on a pending list (!list_empty(&task->running)). When that happens the task is removed from the list while holding the session back_lock, but other task list modification occur under the frwd_lock. That leads to linked list corruption and eventually a panicked system. Rather than back out the session lock split entirely, in order to try and keep some of the performance gains this patch adds another lock to maintain the task lists integrity. Major enterprise supported kernels have been backing out the lock split for while now, thanks to the efforts at IBM where a lab setup has the most reliable reproducer I've seen on this issue. This patch has been tested there successfully. Signed-off-by: Chris Leech Fixes: 659743b02c41 ("[SCSI] libiscsi: Reduce locking contention in fast path") Reported-by: Prashantha Subbarao Reviewed-by: Guilherme G. Piccoli Signed-off-by: Martin K. Petersen Signed-off-by: Greg Kroah-Hartman --- include/scsi/libiscsi.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/scsi') diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h index 4d1c46aac331..c7b1dc713cdd 100644 --- a/include/scsi/libiscsi.h +++ b/include/scsi/libiscsi.h @@ -196,6 +196,7 @@ struct iscsi_conn { struct iscsi_task *task; /* xmit task in progress */ /* xmit */ + spinlock_t taskqueuelock; /* protects the next three lists */ struct list_head mgmtqueue; /* mgmt (control) xmit queue */ struct list_head cmdqueue; /* data-path cmd queue */ struct list_head requeue; /* tasks needing another run */ -- cgit v1.2.3