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authorIan Gudger <igudger@google.com>2019-06-13 17:24:58 -0700
committerShentubot <shentubot@google.com>2019-06-13 17:26:22 -0700
commit0a5ee6f7b20ef4f5533766d753b85005f79ae613 (patch)
tree3ffc2f9ad60ab4ba97e9a924d925f3ff00fd8f5a /pkg/sentry/fs/g3doc/inotify.md
parent05ff1ffaadaa0ac370365eb14febc761506735ce (diff)
Fix deadlock in fasync.
The deadlock can occur when both ends of a connected Unix socket which has FIOASYNC enabled on at least one end are closed at the same time. One end notifies that it is closing, calling (*waiter.Queue).Notify which takes waiter.Queue.mu (as a read lock) and then calls (*FileAsync).Callback, which takes FileAsync.mu. The other end tries to unregister for notifications by calling (*FileAsync).Unregister, which takes FileAsync.mu and calls (*waiter.Queue).EventUnregister which takes waiter.Queue.mu. This is fixed by moving the calls to waiter.Waitable.EventRegister and waiter.Waitable.EventUnregister outside of the protection of any mutex used in (*FileAsync).Callback. The new test is related, but does not cover this particular situation. Also fix a data race on FileAsync.e.Callback. (*FileAsync).Callback checked FileAsync.e.Callback under the protection of FileAsync.mu, but the waiter calling (*FileAsync).Callback could not and did not. This is fixed by making FileAsync.e.Callback immutable before passing it to the waiter for the first time. Fixes #346 PiperOrigin-RevId: 253138340
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