Duncan Coutts pushed to branch wip/io-manager-deadlock-detection at Glasgow Haskell Compiler / GHC

Commits:

• 11004739
  by Duncan Coutts at 2026-07-22T10:39:13+01:00

  FIXUP     Make signal handling be a respondibility of the I/O manager(s)
  
  In select, we need to check for signals when we poll for I/O, as well as
  when select itself gets interupted by a signal. This matches what we do
  in the poll I/O manager.
  

• 46bb53d6
  by Duncan Coutts at 2026-07-22T10:55:06+01:00

  FIXUP:     Clean up the RTS internal signal handling API
  

2 changed files:

• rts/posix/Select.c
• rts/posix/Signals.c

Changes:

     do {

       now = getLowResTimeOfDay();

-      if (wakeUpSleepingThreads(iomgr, now)) {

-          return true;

+      wakeUpSleepingThreads(iomgr, now);

+#if defined(RTS_USER_SIGNALS)

+      startPendingSignalHandlers(iomgr->cap);

+#endif

+      /* If either of the above (checking for timers or signal) caused threads

+       * to be started (or if the run queue was non-empty in the first place),

+       * then poll for I/O but don't block waiting.

+       */

+      if (!emptyRunQueue(iomgr->cap)) {

+          wait = false;

       }

       /*

            // freed by runHandler

     memcpy(info, next_pending_handler, sizeof(siginfo_t));

+    debugTrace(DEBUG_iomanager,

+               "Handling pending signal, no %d", info->si_signo);

+

     StgTSO *t =

         createIOThread(cap,

                        RtsFlags.GcFlags.initialStkSize,