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authorWaiman Long <longman@redhat.com>2020-01-15 10:43:36 -0500
committerPeter Zijlstra <peterz@infradead.org>2020-01-17 10:19:27 +0100
commit39e7234f00bc93613c086ae42d852d5f4147120a (patch)
tree35f22309a78dc484ba8efa5602c58ee468955a9d /kernel
parent51bfb1d11d6daf095addf9fe8471c20992caae0b (diff)
locking/rwsem: Fix kernel crash when spinning on RWSEM_OWNER_UNKNOWN
The commit 91d2a812dfb9 ("locking/rwsem: Make handoff writer optimistically spin on owner") will allow a recently woken up waiting writer to spin on the owner. Unfortunately, if the owner happens to be RWSEM_OWNER_UNKNOWN, the code will incorrectly spin on it leading to a kernel crash. This is fixed by passing the proper non-spinnable bits to rwsem_spin_on_owner() so that RWSEM_OWNER_UNKNOWN will be treated as a non-spinnable target. Fixes: 91d2a812dfb9 ("locking/rwsem: Make handoff writer optimistically spin on owner") Reported-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Christoph Hellwig <hch@lst.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200115154336.8679-1-longman@redhat.com
Diffstat (limited to 'kernel')
-rw-r--r--kernel/locking/rwsem.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 44e68761f432..0d9b6be9ecc8 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -1226,8 +1226,8 @@ wait:
* In this case, we attempt to acquire the lock again
* without sleeping.
*/
- if ((wstate == WRITER_HANDOFF) &&
- (rwsem_spin_on_owner(sem, 0) == OWNER_NULL))
+ if (wstate == WRITER_HANDOFF &&
+ rwsem_spin_on_owner(sem, RWSEM_NONSPINNABLE) == OWNER_NULL)
goto trylock_again;
/* Block until there are no active lockers. */