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authorRoland Dreier <rolandd@cisco.com>2007-06-21 11:05:58 -0700
committerRoland Dreier <rolandd@cisco.com>2007-06-21 11:05:58 -0700
commit24bce5080306bd5255cbda3d6b09a29d5515b470 (patch)
treed0061299531d0cda6bd83196f8f4c32c5f93af15
parentd025d7858f7415f558e89d870ad1a205954b64cd (diff)
IB/umem: Fix possible hang on process exit
If ib_umem_release() is called after ib_uverbs_close() sets context->closing, then a process can get stuck in a D state, because the code boils down to if (down_write_trylock(&mm->mmap_sem)) down_write(&mm->mmap_sem); which is obviously a stupid instant deadlock. Fix the code so that we only try to take the lock once. This bug was introduced in commit f7c6a7b5 ("IB/uverbs: Export ib_umem_get()/ib_umem_release() to modules") which fortunately never made it into a release, and was reported by Pete Wyckoff <pw@osc.edu>. Signed-off-by: Roland Dreier <rolandd@cisco.com>
-rw-r--r--drivers/infiniband/core/umem.c16
1 files changed, 9 insertions, 7 deletions
diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
index b4aec5103c9..d40652a8015 100644
--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -225,13 +225,15 @@ void ib_umem_release(struct ib_umem *umem)
* up here and not be able to take the mmap_sem. In that case
* we defer the vm_locked accounting to the system workqueue.
*/
- if (context->closing && !down_write_trylock(&mm->mmap_sem)) {
- INIT_WORK(&umem->work, ib_umem_account);
- umem->mm = mm;
- umem->diff = diff;
-
- schedule_work(&umem->work);
- return;
+ if (context->closing) {
+ if (!down_write_trylock(&mm->mmap_sem)) {
+ INIT_WORK(&umem->work, ib_umem_account);
+ umem->mm = mm;
+ umem->diff = diff;
+
+ schedule_work(&umem->work);
+ return;
+ }
} else
down_write(&mm->mmap_sem);