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Chris Leech 246760c61d scsi: libiscsi: add lock around task lists to fix list corruption regression 
commit 6f8830f5bb 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 <cleech@redhat.com>
Fixes: 659743b02c ("[SCSI] libiscsi: Reduce locking contention in fast path")
Reported-by: Prashantha Subbarao <psubbara@us.ibm.com>
Reviewed-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-03-26 12:13:19 +02:00
..
acpi Merge branch 'acpi-pci' 2015-11-07 01:30:10 +01:00
asm-generic asm-generic: make copy_from_user() zero the destination properly 2016-09-24 10:07:45 +02:00
clocksource
crypto crypto: ghash-generic - move common definitions to a new header file 2016-10-22 12:26:56 +02:00
drm drm/prime: Pass the right module owner through to dma_buf_export() 2016-10-31 04:13:57 -06:00
dt-bindings ARM: DT updates for v4.4 2015-11-10 15:06:26 -08:00
keys
kvm KVM: arm/arm64: arch_timer: Preserve physical dist. active state on LR.active 2015-11-24 18:07:40 +01:00
linux give up on gcc ilog2() constant optimizations 2017-03-26 12:13:18 +02:00
math-emu
media videobuf2-core: Check user space planes array in dqbuf 2016-05-04 14:48:50 -07:00
memory
misc
net netlabel: out of bound access in cipso_v4_validate() 2017-02-18 16:39:26 +01:00
pcmcia
ras
rdma RDMA/core: Fix incorrect structure packing for booleans 2017-03-12 06:37:29 +01:00
rxrpc
scsi scsi: libiscsi: add lock around task lists to fix list corruption regression 2017-03-26 12:13:19 +02:00
soc ARM: at91: define LPDDR types 2017-03-12 06:37:24 +01:00
sound ALSA: rawmidi: Make snd_rawmidi_transmit() race-free 2016-02-17 12:30:58 -08:00
target target: Fix NULL dereference during LUN lookup + active I/O shutdown 2017-03-15 09:57:14 +08:00
trace tracing: Add #undef to fix compile error 2017-03-18 19:09:57 +08:00
uapi uapi: fix linux/packet_diag.h userspace compilation error 2017-03-22 12:04:16 +01:00
video drm/imx: Match imx-ipuv3-crtc components using device node in platform data 2016-06-07 18:14:37 -07:00
xen xen: Fix page <-> pfn conversion on 32 bit systems 2016-05-11 11:21:14 +02:00
Kbuild