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cxl: Change contexts_lock to a mutex to fix sleep while atomic bug

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We had a known sleep while atomic bug if a CXL device was forcefully
unbound while it was in use. This could occur as a result of EEH, or
manually induced with something like this while the device was in use:

echo 0000:01:00.0 > /sys/bus/pci/drivers/cxl-pci/unbind

The issue was that in this code path we iterated over each context and
forcefully detached it with the contexts_lock spin lock held, however
the detach also needed to take the spu_mutex, and call schedule.

This patch changes the contexts_lock to a mutex so that we are not in
atomic context while doing the detach, thereby avoiding the sleep while
atomic.

Also delete the related TODO comment, which suggested an alternate
solution which turned out to not be workable.

Cc: stable@vger.kernel.org
Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Ian Munsie
2014-12-08 19:17:55 +11:00
committed by Michael Ellerman
parent 7c5c92ed56
commit ee41d11d53
5 changed files with 15 additions and 21 deletions
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2
drivers/misc/cxl/pci.c
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@@ -502,7 +502,7 @@ static struct cxl_afu *cxl_alloc_afu(struct cxl *adapter, int slice)
afu->dev.release = cxl_release_afu;
afu->slice = slice;
idr_init(&afu->contexts_idr);
spin_lock_init(&afu->contexts_lock);
mutex_init(&afu->contexts_lock);
spin_lock_init(&afu->afu_cntl_lock);
mutex_init(&afu->spa_mutex);