Cheng Shao pushed to branch wip/clear-block-info at Glasgow Haskell Compiler / GHC
Commits:
b4b1720d by Ben Gamari at 2025-11-29T23:35:57+01:00
rts: Clear block_info when unblocking
Otherwise we may end up with dangling pointers which may complicate
debugging. Also, introduce more strict checking of block_info in
checkTSO.
Co-authored-by: Cheng Shao
- - - - -
9 changed files:
- rts/RaiseAsync.c
- rts/Schedule.c
- rts/Threads.c
- rts/include/rts/storage/TSO.h
- rts/posix/Poll.c
- rts/posix/Select.c
- rts/posix/Timeout.c
- rts/sm/Sanity.c
- rts/win32/AsyncMIO.c
Changes:
=====================================
rts/RaiseAsync.c
=====================================
@@ -716,12 +716,13 @@ removeFromQueues(Capability *cap, StgTSO *tso)
syncDelayCancel(cap, tso);
goto done;
- default:
+ default:
barf("removeFromQueues: %d", tso->why_blocked);
}
done:
RELAXED_STORE(&tso->why_blocked, NotBlocked);
+ tso->block_info.closure = (StgClosure *)END_TSO_QUEUE;
appendToRunQueue(cap, tso);
}
@@ -1087,6 +1088,7 @@ done:
// wake it up
if (tso->why_blocked != NotBlocked) {
tso->why_blocked = NotBlocked;
+ tso->block_info.closure = (StgClosure *)END_TSO_QUEUE;
appendToRunQueue(cap,tso);
}
=====================================
rts/Schedule.c
=====================================
@@ -2589,7 +2589,8 @@ resumeThread (void *task_)
traceEventRunThread(cap, tso);
/* Reset blocking status */
- tso->why_blocked = NotBlocked;
+ tso->why_blocked = NotBlocked;
+ tso->block_info.closure = (StgClosure *)END_TSO_QUEUE;
if ((tso->flags & TSO_BLOCKEX) == 0) {
// avoid locking the TSO if we don't have to
=====================================
rts/Threads.c
=====================================
@@ -338,6 +338,7 @@ unblock:
// just run the thread now, if the BH is not really available,
// we'll block again.
tso->why_blocked = NotBlocked;
+ tso->block_info.closure = (StgClosure *)END_TSO_QUEUE;
appendToRunQueue(cap,tso);
// We used to set the context switch flag here, which would
=====================================
rts/include/rts/storage/TSO.h
=====================================
@@ -297,8 +297,8 @@ void setTSOPrev (Capability *cap, StgTSO *tso, StgTSO *target);
void dirty_STACK (Capability *cap, StgStack *stack);
/* -----------------------------------------------------------------------------
- Invariants:
-
+ Note [TSO invariants]
+ ~~~~~~~~~~~~~~~~~~~~~
An active thread has the following properties:
tso->stack < tso->sp < tso->stack+tso->stack_size
@@ -313,7 +313,8 @@ void dirty_STACK (Capability *cap, StgStack *stack);
tso->why_blocked tso->block_info location
----------------------------------------------------------------------
- NotBlocked END_TSO_QUEUE runnable_queue, or running
+ NotBlocked END_TSO_QUEUE running
+ NotBlocked prev TSO runnable_queue (block_info.prev back-link)
BlockedOnBlackHole MessageBlackHole * TSO->bq
=====================================
rts/posix/Poll.c
=====================================
@@ -261,6 +261,7 @@ static void notifyIOCompletion(Capability *cap, StgAsyncIOOp *aiop)
*/
StgTSO *tso = aiop->notify.tso;
tso->why_blocked = NotBlocked;
+ tso->block_info.closure = (StgClosure *)END_TSO_QUEUE;
tso->_link = END_TSO_QUEUE;
pushOnRunQueue(cap, tso);
}
=====================================
rts/posix/Select.c
=====================================
@@ -106,6 +106,7 @@ static bool wakeUpSleepingThreads (Capability *cap, LowResTime now)
}
iomgr->sleeping_queue = tso->_link;
RELAXED_STORE(&tso->why_blocked, NotBlocked);
+ tso->block_info.closure = (StgClosure *)END_TSO_QUEUE;
tso->_link = END_TSO_QUEUE;
IF_DEBUG(scheduler, debugBelch("Waking up sleeping thread %"
FMT_StgThreadID "\n", tso->id));
@@ -437,6 +438,7 @@ awaitCompletedTimeoutsOrIOSelect(Capability *cap, bool wait)
debugBelch("Waking up blocked thread %" FMT_StgThreadID "\n",
tso->id));
tso->why_blocked = NotBlocked;
+ tso->block_info.closure = (StgClosure *)END_TSO_QUEUE;
tso->_link = END_TSO_QUEUE;
pushOnRunQueue(cap,tso);
break;
=====================================
rts/posix/Timeout.c
=====================================
@@ -122,6 +122,7 @@ static void notifyTimeoutCompletion(Capability *cap, StgTimeout *timeout)
{
StgTSO *tso = timeout->notify.tso;
tso->why_blocked = NotBlocked;
+ tso->block_info.closure = (StgClosure *)END_TSO_QUEUE;
tso->_link = END_TSO_QUEUE;
pushOnRunQueue(cap, tso);
break;
@@ -226,4 +227,3 @@ struct timespec *timeoutInNanoseconds(CapIOManager *iomgr, bool wait,
#endif
#endif // defined(IOMGR_ENABLED_POLL)
-
=====================================
rts/sm/Sanity.c
=====================================
@@ -767,7 +767,6 @@ checkSTACK (StgStack *stack)
*
* See #19146.
*/
-
void
checkTSO(StgTSO *tso)
{
@@ -788,6 +787,14 @@ checkTSO(StgTSO *tso)
ASSERT(LOOKS_LIKE_CLOSURE_PTR(tso->block_info.closure));
}
+ /* See Note [TSO invariants] in TSO.h */
+ if (tso->why_blocked == NotBlocked) {
+ // When on a run queue we use block_info.prev as the back-link.
+ // Otherwise (running) we expect END_TSO_QUEUE.
+ ASSERT(tso->block_info.closure == (StgClosure *)END_TSO_QUEUE ||
+ get_itbl(tso->block_info.closure)->type == TSO);
+ }
+
ASSERT(LOOKS_LIKE_CLOSURE_PTR(tso->bq));
ASSERT(LOOKS_LIKE_CLOSURE_PTR(tso->blocked_exceptions));
ASSERT(LOOKS_LIKE_CLOSURE_PTR(tso->stackobj));
=====================================
rts/win32/AsyncMIO.c
=====================================
@@ -319,14 +319,16 @@ start:
: END_TSO_QUEUE;
}
- // Terminates the run queue + this inner for-loop.
- tso->_link = END_TSO_QUEUE;
- tso->why_blocked = NotBlocked;
// save the StgAsyncIOResult in the
// stg_block_async_info stack frame, because
// the block_info field will be overwritten by
// pushOnRunQueue().
tso->stackobj->sp[1] = (W_)tso->block_info.async_result;
+
+ tso->why_blocked = NotBlocked;
+ tso->block_info.closure = (StgClosure *)END_TSO_QUEUE;
+ // Terminates the run queue + this inner for-loop.
+ tso->_link = END_TSO_QUEUE;
pushOnRunQueue(&MainCapability, tso);
break;
}
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b4b1720da1fb6e7792dc7779f3d02ad1...
--
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b4b1720da1fb6e7792dc7779f3d02ad1...
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