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| author | Sergei Trofimovich <slyfox@gentoo.org> | 2015-07-07 17:00:23 +0200 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2015-07-07 19:17:43 +0200 |
| commit | 5857e0afb5823987e84e6d3dd8d0b269b7546166 (patch) | |
| tree | 41c3b179e139a19a09dbf605e3a1d4aac6d8b0d7 /rts/posix | |
| parent | 9a3e1657db4c0292fc06d6183a802af631c3666a (diff) | |
| download | haskell-5857e0afb5823987e84e6d3dd8d0b269b7546166.tar.gz | |
fix EBADF unqueueing in select backend (Trac #10590)
Alexander found a interesting case:
1. We have a queue of two waiters in a blocked_queue
2. first file descriptor changes state to RUNNABLE,
second changes to INVALID
3. awaitEvent function dequeued RUNNABLE thread to a
run queue and attempted to dequeue INVALID descriptor
to a run queue.
Unqueueing INVALID fails thusly:
#3 0x000000000045cf1c in barf (s=0x4c1cb0 "removeThreadFromDeQueue: not found")
at rts/RtsMessages.c:42
#4 0x000000000046848b in removeThreadFromDeQueue (...) at rts/Threads.c:249
#5 0x000000000049a120 in removeFromQueues (...) at rts/RaiseAsync.c:719
#6 0x0000000000499502 in throwToSingleThreaded__ (...) at rts/RaiseAsync.c:67
#7 0x0000000000499555 in throwToSingleThreaded (..) at rts/RaiseAsync.c:75
#8 0x000000000047c27d in awaitEvent (wait=rtsFalse) at rts/posix/Select.c:415
The problem here is a throwToSingleThreaded function that tries
to unqueue a TSO from blocked_queue, but awaitEvent function
leaves blocked_queue in a inconsistent state while traverses
over blocked_queue:
case RTS_FD_IS_READY:
IF_DEBUG(scheduler,
debugBelch("Waking up blocked thread %lu\n",
(unsigned long)tso->id));
tso->why_blocked = NotBlocked;
tso->_link = END_TSO_QUEUE; // Here we break the queue head
pushOnRunQueue(&MainCapability,tso);
break;
Signed-off-by: Sergei Trofimovich <siarheit@google.com>
Test Plan: tested on a sample from T10590
Reviewers: austin, bgamari, simonmar
Reviewed By: bgamari, simonmar
Subscribers: qnikst, thomie, bgamari
Differential Revision: https://phabricator.haskell.org/D1024
GHC Trac Issues: #10590, #4934
Diffstat (limited to 'rts/posix')
| -rw-r--r-- | rts/posix/Select.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/rts/posix/Select.c b/rts/posix/Select.c index 4b1923504b..d5c9b553cb 100644 --- a/rts/posix/Select.c +++ b/rts/posix/Select.c @@ -375,6 +375,12 @@ awaitEvent(rtsBool wait) prev = NULL; { + /* + * The queue is being rebuilt in this loop: + * 'blocked_queue_hd' will contain already + * traversed blocked TSOs. As a result you + * can't use functions accessing 'blocked_queue_hd'. + */ for(tso = blocked_queue_hd; tso != END_TSO_QUEUE; tso = next) { next = tso->_link; int fd; @@ -412,8 +418,8 @@ awaitEvent(rtsBool wait) IF_DEBUG(scheduler, debugBelch("Killing blocked thread %lu on bad fd=%i\n", (unsigned long)tso->id, fd)); - throwToSingleThreaded(&MainCapability, tso, - (StgClosure *)blockedOnBadFD_closure); + raiseAsync(&MainCapability, tso, + (StgClosure *)blockedOnBadFD_closure, rtsFalse, NULL); break; case RTS_FD_IS_READY: IF_DEBUG(scheduler, |