894583 - Deadlock in nsCacheService and nsDeleteDir at BlockResourceBase.cpp:125

Status: RESOLVED WONTFIX

(Core :: Networking: Cache, defect)

Description

[Kartikaya Gupta (email:[e-mail])]

From a recent m-c (+unrelated local changes) build:

07-16 16:22:04.042 I/Gecko   ( 5147): ###!!! ASSERTION: Potential deadlock detected:
07-16 16:22:04.042 I/Gecko   ( 5147): Cyclical dependency starts at
07-16 16:22:04.042 I/Gecko   ( 5147): Mutex : nsCacheService.mLock
07-16 16:22:04.042 I/Gecko   ( 5147): Next dependency:
07-16 16:22:04.042 I/Gecko   ( 5147): Mutex : nsDeleteDir.mLock (currently acquired)
07-16 16:22:04.042 I/Gecko   ( 5147): Cycle completed at
07-16 16:22:04.042 I/Gecko   ( 5147): Mutex : nsCacheService.mLock
07-16 16:22:04.042 I/Gecko   ( 5147): Deadlock may happen for some other execution
07-16 16:22:04.042 I/Gecko   ( 5147):
07-16 16:22:04.042 I/Gecko   ( 5147): : 'Error', file /Users/kats/zspace/mozilla-git/obj-android-debug/xpcom/build/BlockingResourceBase.cpp, line 125
07-16 16:22:04.042 I/Gecko   ( 5147): ###!!! ASSERTION: Potential deadlock detected:
07-16 16:22:04.042 I/Gecko   ( 5147): Cyclical dependency starts at
07-16 16:22:04.042 I/Gecko   ( 5147): Mutex : nsCacheService.mLock
07-16 16:22:04.042 I/Gecko   ( 5147): Next dependency:
07-16 16:22:04.042 I/Gecko   ( 5147): Mutex : nsDeleteDir.mLock (currently acquired)
07-16 16:22:04.042 I/Gecko   ( 5147): Cycle completed at
07-16 16:22:04.042 I/Gecko   ( 5147): Mutex : nsCacheService.mLock
07-16 16:22:04.042 I/Gecko   ( 5147): Deadlock may happen for some other execution
07-16 16:22:04.042 I/Gecko   ( 5147):
07-16 16:22:04.042 I/Gecko   ( 5147): : 'Error', file /Users/kats/zspace/mozilla-git/obj-android-debug/xpcom/build/BlockingResourceBase.cpp, line 125
07-16 16:22:04.042 I/Gecko   ( 5147): ###!!! ASSERTION: Potential deadlock detected:
07-16 16:22:04.042 I/Gecko   ( 5147): Cyclical dependency starts at
07-16 16:22:04.042 I/Gecko   ( 5147): Mutex : nsCacheService.mLock
07-16 16:22:04.042 I/Gecko   ( 5147): Next dependency:
07-16 16:22:04.042 I/Gecko   ( 5147): Mutex : nsDeleteDir.mLock (currently acquired)
07-16 16:22:04.042 I/Gecko   ( 5147): Cycle completed at
07-16 16:22:04.042 I/Gecko   ( 5147): Mutex : nsCacheService.mLock
07-16 16:22:04.042 I/Gecko   ( 5147): Deadlock may happen for some other execution
07-16 16:22:04.042 I/Gecko   ( 5147):
07-16 16:22:04.042 I/Gecko   ( 5147): : 'Error', file /Users/kats/zspace/mozilla-git/obj-android-debug/xpcom/build/BlockingResourceBase.cpp, line 125
07-16 16:22:04.042 I/Gecko   ( 5147): WARNING: NS_ENSURE_TRUE(mThread != PR_GetCurrentThread()) failed: file /Users/kats/zspace/mozilla-git/xpcom/threads/nsThread.cpp, line 434
07-16 16:22:04.052 I/Gecko   ( 5147): ###!!! ASSERTION: Potential deadlock detected:
07-16 16:22:04.052 I/Gecko   ( 5147): Cyclical dependency starts at
07-16 16:22:04.052 I/Gecko   ( 5147): Mutex : nsDeleteDir.mLock (currently acquired)
07-16 16:22:04.052 I/Gecko   ( 5147): Cycle completed at
07-16 16:22:04.052 I/Gecko   ( 5147): Mutex : nsDeleteDir.mLock (currently acquired)
07-16 16:22:04.052 I/Gecko   ( 5147):
07-16 16:22:04.052 I/Gecko   ( 5147): ###!!! Deadlock may happen NOW!
07-16 16:22:04.052 I/Gecko   ( 5147):
07-16 16:22:04.052 I/Gecko   ( 5147): : 'Error', file /Users/kats/zspace/mozilla-git/obj-android-debug/xpcom/build/BlockingResourceBase.cpp, line 125

This deadlock appears to have triggered and caused an ANR in Android.

Comment 1

[Patrick McManus [:mcmanus]]

is this limited to cache1?

Comment 2

[Michal Novotny [:michal]]

Yes, this code will be removed together with the old cache. We use nsDeleteDir now in the cache2 only in case we want to remove old cache tree, but AFAICS the deadlock cannot happen in this case because we don't grab nsDeleteDir's lock when we hold nsCacheService's lock.