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authorSimon Marlow <marlowsd@gmail.com>2017-06-03 20:26:13 +0100
committerSimon Marlow <marlowsd@gmail.com>2017-06-08 08:38:09 +0100
commit598472908ebb08f6811b892f285490554c290ae3 (patch)
tree84079aceefe1a7eacda507f104c0f0d4d8c12417 /includes
parentbca56bd040de64315564cdac4b7e943fc8a75ea0 (diff)
downloadhaskell-598472908ebb08f6811b892f285490554c290ae3.tar.gz
Fix a lost-wakeup bug in BLACKHOLE handling (#13751)
Summary: The problem occurred when * Threads A & B evaluate the same thunk * Thread A context-switches, so the thunk gets blackholed * Thread C enters the blackhole, creates a BLOCKING_QUEUE attached to the blackhole and thread A's `tso->bq` queue * Thread B updates the blackhole with a value, overwriting the BLOCKING_QUEUE * We GC, replacing A's update frame with stg_enter_checkbh * Throw an exception in A, which ignores the stg_enter_checkbh frame Now we have C blocked on A's tso->bq queue, but we forgot to check the queue because the stg_enter_checkbh frame has been thrown away by the exception. The solution and alternative designs are discussed in Note [upd-black-hole]. This also exposed a bug in the interpreter, whereby we were sometimes context-switching without calling `threadPaused()`. I've fixed this and added some Notes. Test Plan: * `cd testsuite/tests/concurrent && make slow` * validate Reviewers: niteria, bgamari, austin, erikd Reviewed By: erikd Subscribers: rwbarton, thomie GHC Trac Issues: #13751 Differential Revision: https://phabricator.haskell.org/D3630
Diffstat (limited to 'includes')
-rw-r--r--includes/stg/MiscClosures.h2
1 files changed, 0 insertions, 2 deletions
diff --git a/includes/stg/MiscClosures.h b/includes/stg/MiscClosures.h
index 4e8fe68bd6..76cfbd6c8c 100644
--- a/includes/stg/MiscClosures.h
+++ b/includes/stg/MiscClosures.h
@@ -275,8 +275,6 @@ RTS_FUN_DECL(stg_PAP_apply);
RTS_FUN_DECL(stg_gc_noregs);
-RTS_RET(stg_enter_checkbh);
-
RTS_RET(stg_ret_v);
RTS_RET(stg_ret_p);
RTS_RET(stg_ret_n);