ops: fix deadlock on releasing shared mounts #1355
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Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
hinshun
reviewed
Feb 11, 2020
| delete(r.main.shares, r.key) | ||
| } | ||
| return r.MutableRef.Release(ctx) | ||
| } | ||
|
|
||
| var cacheRefReleaseHijack func() | ||
| var cacheRefCloneHijack func() |
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If we move these to a context value, the tests can be run in parallel.
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Extra code needed for that isn't probably worth it. clone() doesn't even take a context atm.
AkihiroSuda
approved these changes
Feb 21, 2020
hinshun
approved these changes
Feb 21, 2020
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fix #1322
regression from 7b1bae7#diff-0d2115e5c32fba316a7eaa987331881cR228
#1092 added another global lock to protect writes to the global map of shared cache mounts. Because the lock is taken too early if conflicts with the locking order of the release method. In case the first shared cache mount is released at the same time another mount is taken with the same key locks are held in the opposite order leading to a deadlock. This PR fixes the ordering issue and makes sure the global lock is not taken before it is needed, improving the efficiency of the mounts with locking sharing mode.
Refactored code to allow unit tests. Tests added for the deadlock case and for all of the sharing methods.
@cpuguy83