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[GHC] #15427: Calling hs_try_putmvar from an unsafe foreign call can cause the RTS to hang
by GHC 06 Sep '18

06 Sep '18

#15427: Calling hs_try_putmvar from an unsafe foreign call can cause the RTS to hang -------------------------------------+------------------------------------- Reporter: syntheorem | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Runtime | Version: 8.4.3 System | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime crash Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- An unsafe foreign call which calls `hs_try_putmvar` can cause the RTS to hang, preventing any Haskell threads from making progress. However, compiling with `-debug` causes it instead to fail an assertion in the scheduler: {{{ internal error: ASSERTION FAILED: file rts/Schedule.c, line 510 (GHC version 8.4.3 for x86_64_apple_darwin) }}} Here is a minimal test case which reproduces the assertion. It needs to be built with `-debug -threaded` and run with `+RTS -N2` or higher. {{{#!hs import Control.Concurrent (forkIO, threadDelay) import Control.Concurrent.MVar (MVar, newEmptyMVar, takeMVar) import Control.Monad (forever) import Foreign.C.Types (CInt(..)) import Foreign.StablePtr (StablePtr) import GHC.Conc (PrimMVar, newStablePtrPrimMVar) foreign import ccall unsafe hs_try_putmvar :: CInt -> StablePtr PrimMVar -> IO () main = do mvar <- newEmptyMVar forkIO $ forever $ do takeMVar mvar forkIO $ forever $ do sp <- newStablePtrPrimMVar mvar hs_try_putmvar (-1) sp threadDelay 1 -- Let it spin a few times to trigger the bug threadDelay 500 }}} I actually checked out GHC and added this as a test case and did some debugging. The specific assertion that fails is `ASSERT(task->cap == cap)`. This seems to happen because of this code in `hs_try_putmvar`: {{{#!c Task *task = getTask(); // ... ACQUIRE_LOCK(&cap->lock); // If the capability is free, we can perform the tryPutMVar immediately if (cap->running_task == NULL) { cap->running_task = task; task->cap = cap; RELEASE_LOCK(&cap->lock); // ... releaseCapability(cap); } else { // ... } }}} Basically it assumes that the current thread's task isn't currently running a capability, so it takes a new one and then releases it without restoring the previous value of `task->cap`. Modifying the code to restore the value of `task->cap` after releasing the capability fixes the assertion. But I don't know enough about the RTS to be sure I'm not missing something here. In particular, is there a problem with the task basically holding two capabilities for a short time? My other thought is that maybe it should check if its task is currently running a capability, and in that case do something else. But I'm not sure what. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15427> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13499: "Panic: no skolem info" with StaticPointers and typed hole
by GHC 06 Sep '18

06 Sep '18

#13499: "Panic: no skolem info" with StaticPointers and typed hole -------------------------------------+------------------------------------- Reporter: Otini | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Linux StaticPointers, hole, skolem, | panic | Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When compiling this minimal example: {{{#!hs {-# LANGUAGE GADTs #-} {-# LANGUAGE StaticPointers #-} import Data.Typeable (Typeable) import GHC.StaticPtr (StaticPtr) f :: Typeable a => StaticPtr (a -> a) f = static (\a -> _) main :: IO () main = return () }}} I get this output: {{{ Bug.hs:8:19: error:ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): No skolem info: a_aJo[sk] Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} Unlike similar reported bugs, this happens on both 8.0.1 and 8.0.2. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13499> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #3372: Allow for multiple linker instances
by GHC 06 Sep '18

06 Sep '18

#3372: Allow for multiple linker instances -------------------------------------+------------------------------------- Reporter: jcpetruzza | Owner: (none) Type: feature request | Status: new Priority: low | Milestone: Component: Runtime System | Version: (Linker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: 3658 | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by gelisam): I believe this has been fixed in ghc 7.10.1, can we close this? At least, the release notes for ghc 7.10.1 claim that the linker API is now thread-safe: https://downloads.haskell.org/~ghc/7.10.1/docs/html/users_guide/release-7-1… See https://github.com/mvdan/hint/issues/68#issuecomment-419088813 for the rest of my archeological search on the history of this ticket and why I believe this is now fixed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3372#comment:18> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15587: traceEvent tests failing in slow validate
by GHC 06 Sep '18

06 Sep '18

#15587: traceEvent tests failing in slow validate -------------------------------------+------------------------------------- Reporter: osa1 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Test Suite | Version: 8.5 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): Phab:D5119 | Wiki Page: -------------------------------------+------------------------------------- traceEvent tests are failing in slow validate when testing in GHCi way: {{{ =====> traceEvent(ghci) 1 of 2 [0, 0, 0] cd "rts/traceEvent.run" && "/home/omer/haskell/ghc/inplace/test spaces /ghc-stage2" traceEvent.hs -dcore-lint -dcmm-lint -no-user-package-db -rtsopts -fno-warn-missed-specialisations -fshow-warning-groups -fdiagnostics-color=never -fno-diagnostics-show-caret -dno-debug-output --interactive -v0 -ignore-dot-ghci -fno-ghci-history +RTS -I0.1 -RTS -eventlog< traceEvent.genscript Actual stderr output differs from expected: diff -uw "rts/traceEvent.run/traceEvent.stderr.normalised" "rts/traceEvent.run/traceEvent.run.stderr.normalised" --- rts/traceEvent.run/traceEvent.stderr.normalised 2018-08-31 12:48:13.548375420 +0300 +++ rts/traceEvent.run/traceEvent.run.stderr.normalised 2018-08-31 12:48:13.548375420 +0300 @@ -1 +0,0 @@ -traceEvent: Event size exceeds EVENT_PAYLOAD_SIZE_MAX, bail out *** unexpected failure for traceEvent(ghci) =====> traceBinaryEvent(ghci) 2 of 2 [0, 1, 0] cd "rts/traceBinaryEvent.run" && "/home/omer/haskell/ghc/inplace/test spaces/ghc-stage2" traceBinaryEvent.hs -dcore-lint -dcmm-lint -no-user- package-db -rtsopts -fno-warn-missed-specialisations -fshow-warning-groups -fdiagnostics-color=never -fno-diagnostics-show-caret -dno-debug-output --interactive -v0 -ignore-dot-ghci -fno-ghci-history +RTS -I0.1 -RTS -eventlog< traceBinaryEvent.genscript Actual stderr output differs from expected: diff -uw "rts/traceBinaryEvent.run/traceBinaryEvent.stderr.normalised" "rts/traceBinaryEvent.run/traceBinaryEvent.run.stderr.normalised" --- rts/traceBinaryEvent.run/traceBinaryEvent.stderr.normalised 2018-08-31 12:48:13.712373185 +0300 +++ rts/traceBinaryEvent.run/traceBinaryEvent.run.stderr.normalised 2018-08-31 12:48:13.712373185 +0300 @@ -1 +0,0 @@ -traceBinaryEvent: Event size exceeds EVENT_PAYLOAD_SIZE_MAX, bail out *** unexpected failure for traceBinaryEvent(ghci) Unexpected results from: TEST="traceBinaryEvent traceEvent" }}} I think GHCi doesn't generate eventlogs so there's no way to make these pass. I submitted Phab:D5119 to skip these tests in GHCi way. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15587> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7: dodgy case of unboxed tuple type
by GHC 06 Sep '18

06 Sep '18

#7: dodgy case of unboxed tuple type --------------------------------+-------------------- Reporter: mtehver | Owner: nobody Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 5.02 Resolution: Fixed | Keywords: Type of failure: None/Unknown | --------------------------------+-------------------- Changes (by Ömer Sinan Ağacan <omeragacan@…>): * failure: => None/Unknown Comment: In [changeset:"c6fbac6a6a69a2f4be89701b2c386ae53214f9a3/ghc" c6fbac6/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="c6fbac6a6a69a2f4be89701b2c386ae53214f9a3" Fix a race between GC threads in concurrent scavenging While debugging #15285 I realized that free block lists (free_list in BlockAlloc.c) get corrupted when multiple scavenge threads allocate and release blocks concurrently. Here's a picture of one such race: Thread 2 (Thread 32573.32601): #0 check_tail (bd=0x940d40 <stg_TSO_info>) at rts/sm/BlockAlloc.c:860 #1 0x0000000000928ef7 in checkFreeListSanity () at rts/sm/BlockAlloc.c:896 #2 0x0000000000928979 in freeGroup (p=0x7e998ce02880) at rts/sm/BlockAlloc.c:721 #3 0x0000000000928a17 in freeChain (bd=0x7e998ce02880) at rts/sm/BlockAlloc.c:738 #4 0x0000000000926911 in freeChain_sync (bd=0x7e998ce02880) at rts/sm/GCUtils.c:80 #5 0x0000000000934720 in scavenge_capability_mut_lists (cap=0x1acae80) at rts/sm/Scav.c:1665 #6 0x000000000092b411 in gcWorkerThread (cap=0x1acae80) at rts/sm/GC.c:1157 #7 0x000000000090be9a in yieldCapability (pCap=0x7f9994e69e20, task=0x7e9984000b70, gcAllowed=true) at rts/Capability.c:861 #8 0x0000000000906120 in scheduleYield (pcap=0x7f9994e69e50, task=0x7e9984000b70) at rts/Schedule.c:673 #9 0x0000000000905500 in schedule (initialCapability=0x1acae80, task=0x7e9984000b70) at rts/Schedule.c:293 #10 0x0000000000908d4f in scheduleWorker (cap=0x1acae80, task=0x7e9984000b70) at rts/Schedule.c:2554 #11 0x000000000091a30a in workerStart (task=0x7e9984000b70) at rts/Task.c:444 #12 0x00007f99937fa6db in start_thread (arg=0x7f9994e6a700) at pthread_create.c:463 #13 0x000061654d59f88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95 Thread 1 (Thread 32573.32573): #0 checkFreeListSanity () at rts/sm/BlockAlloc.c:887 #1 0x0000000000928979 in freeGroup (p=0x7e998d303540) at rts/sm/BlockAlloc.c:721 #2 0x0000000000926f23 in todo_block_full (size=513, ws=0x1aa8ce0) at rts/sm/GCUtils.c:264 #3 0x00000000009583b9 in alloc_for_copy (size=513, gen_no=0) at rts/sm/Evac.c:80 #4 0x000000000095850d in copy_tag_nolock (p=0x7e998c675f28, info=0x421d98 <Main_Large_con_info>, src=0x7e998d075d80, size=513, gen_no=0, tag=1) at rts/sm/Evac.c:153 #5 0x0000000000959177 in evacuate (p=0x7e998c675f28) at rts/sm/Evac.c:715 #6 0x0000000000932388 in scavenge_small_bitmap (p=0x7e998c675f28, size=1, bitmap=0) at rts/sm/Scav.c:271 #7 0x0000000000934aaf in scavenge_stack (p=0x7e998c675f28, stack_end=0x7e998c676000) at rts/sm/Scav.c:1908 #8 0x0000000000934295 in scavenge_one (p=0x7e998c66e000) at rts/sm/Scav.c:1466 #9 0x0000000000934662 in scavenge_mutable_list (bd=0x7e998d300440, gen=0x1b1d880) at rts/sm/Scav.c:1643 #10 0x0000000000934700 in scavenge_capability_mut_lists (cap=0x1aaa340) at rts/sm/Scav.c:1664 #11 0x00000000009299b6 in GarbageCollect (collect_gen=0, do_heap_census=false, gc_type=2, cap=0x1aaa340, idle_cap=0x1b38aa0) at rts/sm/GC.c:378 #12 0x0000000000907a4a in scheduleDoGC (pcap=0x7ffdec5b5310, task=0x1b36650, force_major=false) at rts/Schedule.c:1798 #13 0x0000000000905de7 in schedule (initialCapability=0x1aaa340, task=0x1b36650) at rts/Schedule.c:546 #14 0x0000000000908bc4 in scheduleWaitThread (tso=0x7e998c0067c8, ret=0x0, pcap=0x7ffdec5b5430) at rts/Schedule.c:2537 #15 0x000000000091b5a0 in rts_evalLazyIO (cap=0x7ffdec5b5430, p=0x9c11f0, ret=0x0) at rts/RtsAPI.c:530 #16 0x000000000091ca56 in hs_main (argc=1, argv=0x7ffdec5b5628, main_closure=0x9c11f0, rts_config=...) at rts/RtsMain.c:72 #17 0x0000000000421ea0 in main () In particular, dbl_link_onto() which is used to add a freed block to a doubly-linked free list is not thread safe and corrupts the list when called concurrently. Note that thread 1 is to blame here as thread 2 is properly taking the spinlock. With this patch we now take the spinlock when freeing a todo block in GC, avoiding this race. Test Plan: - Tried slow validate locally: this patch does not introduce new failures. - circleci: https://circleci.com/gh/ghc/ghc-diffs/283 The test got killed because it took 5 hours but T7919 (which was previously failing on circleci) passed. Reviewers: simonmar, bgamari, erikd Reviewed By: simonmar Subscribers: rwbarton, carter GHC Trac Issues: #15285 Differential Revision: https://phabricator.haskell.org/D5115 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7#comment:3> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #9: GHCI for Win32 crashes with many options
by GHC 06 Sep '18

06 Sep '18

#9: GHCI for Win32 crashes with many options --------------------------------+-------------------- Reporter: fizzgig | Owner: nobody Type: bug | Status: closed Priority: normal | Milestone: Component: None | Version: 5.02 Resolution: Fixed | Keywords: Type of failure: None/Unknown | --------------------------------+-------------------- Changes (by Ömer Sinan Ağacan <omeragacan@…>): * failure: => None/Unknown Comment: In [changeset:"c6fbac6a6a69a2f4be89701b2c386ae53214f9a3/ghc" c6fbac6/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="c6fbac6a6a69a2f4be89701b2c386ae53214f9a3" Fix a race between GC threads in concurrent scavenging While debugging #15285 I realized that free block lists (free_list in BlockAlloc.c) get corrupted when multiple scavenge threads allocate and release blocks concurrently. Here's a picture of one such race: Thread 2 (Thread 32573.32601): #0 check_tail (bd=0x940d40 <stg_TSO_info>) at rts/sm/BlockAlloc.c:860 #1 0x0000000000928ef7 in checkFreeListSanity () at rts/sm/BlockAlloc.c:896 #2 0x0000000000928979 in freeGroup (p=0x7e998ce02880) at rts/sm/BlockAlloc.c:721 #3 0x0000000000928a17 in freeChain (bd=0x7e998ce02880) at rts/sm/BlockAlloc.c:738 #4 0x0000000000926911 in freeChain_sync (bd=0x7e998ce02880) at rts/sm/GCUtils.c:80 #5 0x0000000000934720 in scavenge_capability_mut_lists (cap=0x1acae80) at rts/sm/Scav.c:1665 #6 0x000000000092b411 in gcWorkerThread (cap=0x1acae80) at rts/sm/GC.c:1157 #7 0x000000000090be9a in yieldCapability (pCap=0x7f9994e69e20, task=0x7e9984000b70, gcAllowed=true) at rts/Capability.c:861 #8 0x0000000000906120 in scheduleYield (pcap=0x7f9994e69e50, task=0x7e9984000b70) at rts/Schedule.c:673 #9 0x0000000000905500 in schedule (initialCapability=0x1acae80, task=0x7e9984000b70) at rts/Schedule.c:293 #10 0x0000000000908d4f in scheduleWorker (cap=0x1acae80, task=0x7e9984000b70) at rts/Schedule.c:2554 #11 0x000000000091a30a in workerStart (task=0x7e9984000b70) at rts/Task.c:444 #12 0x00007f99937fa6db in start_thread (arg=0x7f9994e6a700) at pthread_create.c:463 #13 0x000061654d59f88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95 Thread 1 (Thread 32573.32573): #0 checkFreeListSanity () at rts/sm/BlockAlloc.c:887 #1 0x0000000000928979 in freeGroup (p=0x7e998d303540) at rts/sm/BlockAlloc.c:721 #2 0x0000000000926f23 in todo_block_full (size=513, ws=0x1aa8ce0) at rts/sm/GCUtils.c:264 #3 0x00000000009583b9 in alloc_for_copy (size=513, gen_no=0) at rts/sm/Evac.c:80 #4 0x000000000095850d in copy_tag_nolock (p=0x7e998c675f28, info=0x421d98 <Main_Large_con_info>, src=0x7e998d075d80, size=513, gen_no=0, tag=1) at rts/sm/Evac.c:153 #5 0x0000000000959177 in evacuate (p=0x7e998c675f28) at rts/sm/Evac.c:715 #6 0x0000000000932388 in scavenge_small_bitmap (p=0x7e998c675f28, size=1, bitmap=0) at rts/sm/Scav.c:271 #7 0x0000000000934aaf in scavenge_stack (p=0x7e998c675f28, stack_end=0x7e998c676000) at rts/sm/Scav.c:1908 #8 0x0000000000934295 in scavenge_one (p=0x7e998c66e000) at rts/sm/Scav.c:1466 #9 0x0000000000934662 in scavenge_mutable_list (bd=0x7e998d300440, gen=0x1b1d880) at rts/sm/Scav.c:1643 #10 0x0000000000934700 in scavenge_capability_mut_lists (cap=0x1aaa340) at rts/sm/Scav.c:1664 #11 0x00000000009299b6 in GarbageCollect (collect_gen=0, do_heap_census=false, gc_type=2, cap=0x1aaa340, idle_cap=0x1b38aa0) at rts/sm/GC.c:378 #12 0x0000000000907a4a in scheduleDoGC (pcap=0x7ffdec5b5310, task=0x1b36650, force_major=false) at rts/Schedule.c:1798 #13 0x0000000000905de7 in schedule (initialCapability=0x1aaa340, task=0x1b36650) at rts/Schedule.c:546 #14 0x0000000000908bc4 in scheduleWaitThread (tso=0x7e998c0067c8, ret=0x0, pcap=0x7ffdec5b5430) at rts/Schedule.c:2537 #15 0x000000000091b5a0 in rts_evalLazyIO (cap=0x7ffdec5b5430, p=0x9c11f0, ret=0x0) at rts/RtsAPI.c:530 #16 0x000000000091ca56 in hs_main (argc=1, argv=0x7ffdec5b5628, main_closure=0x9c11f0, rts_config=...) at rts/RtsMain.c:72 #17 0x0000000000421ea0 in main () In particular, dbl_link_onto() which is used to add a freed block to a doubly-linked free list is not thread safe and corrupts the list when called concurrently. Note that thread 1 is to blame here as thread 2 is properly taking the spinlock. With this patch we now take the spinlock when freeing a todo block in GC, avoiding this race. Test Plan: - Tried slow validate locally: this patch does not introduce new failures. - circleci: https://circleci.com/gh/ghc/ghc-diffs/283 The test got killed because it took 5 hours but T7919 (which was previously failing on circleci) passed. Reviewers: simonmar, bgamari, erikd Reviewed By: simonmar Subscribers: rwbarton, carter GHC Trac Issues: #15285 Differential Revision: https://phabricator.haskell.org/D5115 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9#comment:3> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #8: Regex failure
by GHC 06 Sep '18

06 Sep '18

#8: Regex failure --------------------------------+---------------------- Reporter: xoltar | Owner: simonmar Type: bug | Status: closed Priority: normal | Milestone: Component: hslibs/text | Version: 5.02 Resolution: Fixed | Keywords: Type of failure: None/Unknown | --------------------------------+---------------------- Changes (by Ömer Sinan Ağacan <omeragacan@…>): * failure: => None/Unknown Comment: In [changeset:"c6fbac6a6a69a2f4be89701b2c386ae53214f9a3/ghc" c6fbac6/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="c6fbac6a6a69a2f4be89701b2c386ae53214f9a3" Fix a race between GC threads in concurrent scavenging While debugging #15285 I realized that free block lists (free_list in BlockAlloc.c) get corrupted when multiple scavenge threads allocate and release blocks concurrently. Here's a picture of one such race: Thread 2 (Thread 32573.32601): #0 check_tail (bd=0x940d40 <stg_TSO_info>) at rts/sm/BlockAlloc.c:860 #1 0x0000000000928ef7 in checkFreeListSanity () at rts/sm/BlockAlloc.c:896 #2 0x0000000000928979 in freeGroup (p=0x7e998ce02880) at rts/sm/BlockAlloc.c:721 #3 0x0000000000928a17 in freeChain (bd=0x7e998ce02880) at rts/sm/BlockAlloc.c:738 #4 0x0000000000926911 in freeChain_sync (bd=0x7e998ce02880) at rts/sm/GCUtils.c:80 #5 0x0000000000934720 in scavenge_capability_mut_lists (cap=0x1acae80) at rts/sm/Scav.c:1665 #6 0x000000000092b411 in gcWorkerThread (cap=0x1acae80) at rts/sm/GC.c:1157 #7 0x000000000090be9a in yieldCapability (pCap=0x7f9994e69e20, task=0x7e9984000b70, gcAllowed=true) at rts/Capability.c:861 #8 0x0000000000906120 in scheduleYield (pcap=0x7f9994e69e50, task=0x7e9984000b70) at rts/Schedule.c:673 #9 0x0000000000905500 in schedule (initialCapability=0x1acae80, task=0x7e9984000b70) at rts/Schedule.c:293 #10 0x0000000000908d4f in scheduleWorker (cap=0x1acae80, task=0x7e9984000b70) at rts/Schedule.c:2554 #11 0x000000000091a30a in workerStart (task=0x7e9984000b70) at rts/Task.c:444 #12 0x00007f99937fa6db in start_thread (arg=0x7f9994e6a700) at pthread_create.c:463 #13 0x000061654d59f88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95 Thread 1 (Thread 32573.32573): #0 checkFreeListSanity () at rts/sm/BlockAlloc.c:887 #1 0x0000000000928979 in freeGroup (p=0x7e998d303540) at rts/sm/BlockAlloc.c:721 #2 0x0000000000926f23 in todo_block_full (size=513, ws=0x1aa8ce0) at rts/sm/GCUtils.c:264 #3 0x00000000009583b9 in alloc_for_copy (size=513, gen_no=0) at rts/sm/Evac.c:80 #4 0x000000000095850d in copy_tag_nolock (p=0x7e998c675f28, info=0x421d98 <Main_Large_con_info>, src=0x7e998d075d80, size=513, gen_no=0, tag=1) at rts/sm/Evac.c:153 #5 0x0000000000959177 in evacuate (p=0x7e998c675f28) at rts/sm/Evac.c:715 #6 0x0000000000932388 in scavenge_small_bitmap (p=0x7e998c675f28, size=1, bitmap=0) at rts/sm/Scav.c:271 #7 0x0000000000934aaf in scavenge_stack (p=0x7e998c675f28, stack_end=0x7e998c676000) at rts/sm/Scav.c:1908 #8 0x0000000000934295 in scavenge_one (p=0x7e998c66e000) at rts/sm/Scav.c:1466 #9 0x0000000000934662 in scavenge_mutable_list (bd=0x7e998d300440, gen=0x1b1d880) at rts/sm/Scav.c:1643 #10 0x0000000000934700 in scavenge_capability_mut_lists (cap=0x1aaa340) at rts/sm/Scav.c:1664 #11 0x00000000009299b6 in GarbageCollect (collect_gen=0, do_heap_census=false, gc_type=2, cap=0x1aaa340, idle_cap=0x1b38aa0) at rts/sm/GC.c:378 #12 0x0000000000907a4a in scheduleDoGC (pcap=0x7ffdec5b5310, task=0x1b36650, force_major=false) at rts/Schedule.c:1798 #13 0x0000000000905de7 in schedule (initialCapability=0x1aaa340, task=0x1b36650) at rts/Schedule.c:546 #14 0x0000000000908bc4 in scheduleWaitThread (tso=0x7e998c0067c8, ret=0x0, pcap=0x7ffdec5b5430) at rts/Schedule.c:2537 #15 0x000000000091b5a0 in rts_evalLazyIO (cap=0x7ffdec5b5430, p=0x9c11f0, ret=0x0) at rts/RtsAPI.c:530 #16 0x000000000091ca56 in hs_main (argc=1, argv=0x7ffdec5b5628, main_closure=0x9c11f0, rts_config=...) at rts/RtsMain.c:72 #17 0x0000000000421ea0 in main () In particular, dbl_link_onto() which is used to add a freed block to a doubly-linked free list is not thread safe and corrupts the list when called concurrently. Note that thread 1 is to blame here as thread 2 is properly taking the spinlock. With this patch we now take the spinlock when freeing a todo block in GC, avoiding this race. Test Plan: - Tried slow validate locally: this patch does not introduce new failures. - circleci: https://circleci.com/gh/ghc/ghc-diffs/283 The test got killed because it took 5 hours but T7919 (which was previously failing on circleci) passed. Reviewers: simonmar, bgamari, erikd Reviewed By: simonmar Subscribers: rwbarton, carter GHC Trac Issues: #15285 Differential Revision: https://phabricator.haskell.org/D5115 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8#comment:4> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #10: undefined reference to `Main_main_closur
by GHC 06 Sep '18

06 Sep '18

#10: undefined reference to `Main_main_closur --------------------------------+-------------------- Reporter: nobody | Owner: nobody Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 5.02 Resolution: Invalid | Keywords: Type of failure: None/Unknown | --------------------------------+-------------------- Changes (by Ömer Sinan Ağacan <omeragacan@…>): * failure: => None/Unknown Comment: In [changeset:"c6fbac6a6a69a2f4be89701b2c386ae53214f9a3/ghc" c6fbac6/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="c6fbac6a6a69a2f4be89701b2c386ae53214f9a3" Fix a race between GC threads in concurrent scavenging While debugging #15285 I realized that free block lists (free_list in BlockAlloc.c) get corrupted when multiple scavenge threads allocate and release blocks concurrently. Here's a picture of one such race: Thread 2 (Thread 32573.32601): #0 check_tail (bd=0x940d40 <stg_TSO_info>) at rts/sm/BlockAlloc.c:860 #1 0x0000000000928ef7 in checkFreeListSanity () at rts/sm/BlockAlloc.c:896 #2 0x0000000000928979 in freeGroup (p=0x7e998ce02880) at rts/sm/BlockAlloc.c:721 #3 0x0000000000928a17 in freeChain (bd=0x7e998ce02880) at rts/sm/BlockAlloc.c:738 #4 0x0000000000926911 in freeChain_sync (bd=0x7e998ce02880) at rts/sm/GCUtils.c:80 #5 0x0000000000934720 in scavenge_capability_mut_lists (cap=0x1acae80) at rts/sm/Scav.c:1665 #6 0x000000000092b411 in gcWorkerThread (cap=0x1acae80) at rts/sm/GC.c:1157 #7 0x000000000090be9a in yieldCapability (pCap=0x7f9994e69e20, task=0x7e9984000b70, gcAllowed=true) at rts/Capability.c:861 #8 0x0000000000906120 in scheduleYield (pcap=0x7f9994e69e50, task=0x7e9984000b70) at rts/Schedule.c:673 #9 0x0000000000905500 in schedule (initialCapability=0x1acae80, task=0x7e9984000b70) at rts/Schedule.c:293 #10 0x0000000000908d4f in scheduleWorker (cap=0x1acae80, task=0x7e9984000b70) at rts/Schedule.c:2554 #11 0x000000000091a30a in workerStart (task=0x7e9984000b70) at rts/Task.c:444 #12 0x00007f99937fa6db in start_thread (arg=0x7f9994e6a700) at pthread_create.c:463 #13 0x000061654d59f88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95 Thread 1 (Thread 32573.32573): #0 checkFreeListSanity () at rts/sm/BlockAlloc.c:887 #1 0x0000000000928979 in freeGroup (p=0x7e998d303540) at rts/sm/BlockAlloc.c:721 #2 0x0000000000926f23 in todo_block_full (size=513, ws=0x1aa8ce0) at rts/sm/GCUtils.c:264 #3 0x00000000009583b9 in alloc_for_copy (size=513, gen_no=0) at rts/sm/Evac.c:80 #4 0x000000000095850d in copy_tag_nolock (p=0x7e998c675f28, info=0x421d98 <Main_Large_con_info>, src=0x7e998d075d80, size=513, gen_no=0, tag=1) at rts/sm/Evac.c:153 #5 0x0000000000959177 in evacuate (p=0x7e998c675f28) at rts/sm/Evac.c:715 #6 0x0000000000932388 in scavenge_small_bitmap (p=0x7e998c675f28, size=1, bitmap=0) at rts/sm/Scav.c:271 #7 0x0000000000934aaf in scavenge_stack (p=0x7e998c675f28, stack_end=0x7e998c676000) at rts/sm/Scav.c:1908 #8 0x0000000000934295 in scavenge_one (p=0x7e998c66e000) at rts/sm/Scav.c:1466 #9 0x0000000000934662 in scavenge_mutable_list (bd=0x7e998d300440, gen=0x1b1d880) at rts/sm/Scav.c:1643 #10 0x0000000000934700 in scavenge_capability_mut_lists (cap=0x1aaa340) at rts/sm/Scav.c:1664 #11 0x00000000009299b6 in GarbageCollect (collect_gen=0, do_heap_census=false, gc_type=2, cap=0x1aaa340, idle_cap=0x1b38aa0) at rts/sm/GC.c:378 #12 0x0000000000907a4a in scheduleDoGC (pcap=0x7ffdec5b5310, task=0x1b36650, force_major=false) at rts/Schedule.c:1798 #13 0x0000000000905de7 in schedule (initialCapability=0x1aaa340, task=0x1b36650) at rts/Schedule.c:546 #14 0x0000000000908bc4 in scheduleWaitThread (tso=0x7e998c0067c8, ret=0x0, pcap=0x7ffdec5b5430) at rts/Schedule.c:2537 #15 0x000000000091b5a0 in rts_evalLazyIO (cap=0x7ffdec5b5430, p=0x9c11f0, ret=0x0) at rts/RtsAPI.c:530 #16 0x000000000091ca56 in hs_main (argc=1, argv=0x7ffdec5b5628, main_closure=0x9c11f0, rts_config=...) at rts/RtsMain.c:72 #17 0x0000000000421ea0 in main () In particular, dbl_link_onto() which is used to add a freed block to a doubly-linked free list is not thread safe and corrupts the list when called concurrently. Note that thread 1 is to blame here as thread 2 is properly taking the spinlock. With this patch we now take the spinlock when freeing a todo block in GC, avoiding this race. Test Plan: - Tried slow validate locally: this patch does not introduce new failures. - circleci: https://circleci.com/gh/ghc/ghc-diffs/283 The test got killed because it took 5 hours but T7919 (which was previously failing on circleci) passed. Reviewers: simonmar, bgamari, erikd Reviewed By: simonmar Subscribers: rwbarton, carter GHC Trac Issues: #15285 Differential Revision: https://phabricator.haskell.org/D5115 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10#comment:5> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #11: No error from --make -o out when no main
by GHC 06 Sep '18

06 Sep '18

#11: No error from --make -o out when no main --------------------------------+---------------------- Reporter: rrt | Owner: simonmar Type: bug | Status: closed Priority: normal | Milestone: Component: None | Version: None Resolution: Fixed | Keywords: Type of failure: None/Unknown | --------------------------------+---------------------- Changes (by Ömer Sinan Ağacan <omeragacan@…>): * failure: => None/Unknown Comment: In [changeset:"c6fbac6a6a69a2f4be89701b2c386ae53214f9a3/ghc" c6fbac6/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="c6fbac6a6a69a2f4be89701b2c386ae53214f9a3" Fix a race between GC threads in concurrent scavenging While debugging #15285 I realized that free block lists (free_list in BlockAlloc.c) get corrupted when multiple scavenge threads allocate and release blocks concurrently. Here's a picture of one such race: Thread 2 (Thread 32573.32601): #0 check_tail (bd=0x940d40 <stg_TSO_info>) at rts/sm/BlockAlloc.c:860 #1 0x0000000000928ef7 in checkFreeListSanity () at rts/sm/BlockAlloc.c:896 #2 0x0000000000928979 in freeGroup (p=0x7e998ce02880) at rts/sm/BlockAlloc.c:721 #3 0x0000000000928a17 in freeChain (bd=0x7e998ce02880) at rts/sm/BlockAlloc.c:738 #4 0x0000000000926911 in freeChain_sync (bd=0x7e998ce02880) at rts/sm/GCUtils.c:80 #5 0x0000000000934720 in scavenge_capability_mut_lists (cap=0x1acae80) at rts/sm/Scav.c:1665 #6 0x000000000092b411 in gcWorkerThread (cap=0x1acae80) at rts/sm/GC.c:1157 #7 0x000000000090be9a in yieldCapability (pCap=0x7f9994e69e20, task=0x7e9984000b70, gcAllowed=true) at rts/Capability.c:861 #8 0x0000000000906120 in scheduleYield (pcap=0x7f9994e69e50, task=0x7e9984000b70) at rts/Schedule.c:673 #9 0x0000000000905500 in schedule (initialCapability=0x1acae80, task=0x7e9984000b70) at rts/Schedule.c:293 #10 0x0000000000908d4f in scheduleWorker (cap=0x1acae80, task=0x7e9984000b70) at rts/Schedule.c:2554 #11 0x000000000091a30a in workerStart (task=0x7e9984000b70) at rts/Task.c:444 #12 0x00007f99937fa6db in start_thread (arg=0x7f9994e6a700) at pthread_create.c:463 #13 0x000061654d59f88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95 Thread 1 (Thread 32573.32573): #0 checkFreeListSanity () at rts/sm/BlockAlloc.c:887 #1 0x0000000000928979 in freeGroup (p=0x7e998d303540) at rts/sm/BlockAlloc.c:721 #2 0x0000000000926f23 in todo_block_full (size=513, ws=0x1aa8ce0) at rts/sm/GCUtils.c:264 #3 0x00000000009583b9 in alloc_for_copy (size=513, gen_no=0) at rts/sm/Evac.c:80 #4 0x000000000095850d in copy_tag_nolock (p=0x7e998c675f28, info=0x421d98 <Main_Large_con_info>, src=0x7e998d075d80, size=513, gen_no=0, tag=1) at rts/sm/Evac.c:153 #5 0x0000000000959177 in evacuate (p=0x7e998c675f28) at rts/sm/Evac.c:715 #6 0x0000000000932388 in scavenge_small_bitmap (p=0x7e998c675f28, size=1, bitmap=0) at rts/sm/Scav.c:271 #7 0x0000000000934aaf in scavenge_stack (p=0x7e998c675f28, stack_end=0x7e998c676000) at rts/sm/Scav.c:1908 #8 0x0000000000934295 in scavenge_one (p=0x7e998c66e000) at rts/sm/Scav.c:1466 #9 0x0000000000934662 in scavenge_mutable_list (bd=0x7e998d300440, gen=0x1b1d880) at rts/sm/Scav.c:1643 #10 0x0000000000934700 in scavenge_capability_mut_lists (cap=0x1aaa340) at rts/sm/Scav.c:1664 #11 0x00000000009299b6 in GarbageCollect (collect_gen=0, do_heap_census=false, gc_type=2, cap=0x1aaa340, idle_cap=0x1b38aa0) at rts/sm/GC.c:378 #12 0x0000000000907a4a in scheduleDoGC (pcap=0x7ffdec5b5310, task=0x1b36650, force_major=false) at rts/Schedule.c:1798 #13 0x0000000000905de7 in schedule (initialCapability=0x1aaa340, task=0x1b36650) at rts/Schedule.c:546 #14 0x0000000000908bc4 in scheduleWaitThread (tso=0x7e998c0067c8, ret=0x0, pcap=0x7ffdec5b5430) at rts/Schedule.c:2537 #15 0x000000000091b5a0 in rts_evalLazyIO (cap=0x7ffdec5b5430, p=0x9c11f0, ret=0x0) at rts/RtsAPI.c:530 #16 0x000000000091ca56 in hs_main (argc=1, argv=0x7ffdec5b5628, main_closure=0x9c11f0, rts_config=...) at rts/RtsMain.c:72 #17 0x0000000000421ea0 in main () In particular, dbl_link_onto() which is used to add a freed block to a doubly-linked free list is not thread safe and corrupts the list when called concurrently. Note that thread 1 is to blame here as thread 2 is properly taking the spinlock. With this patch we now take the spinlock when freeing a todo block in GC, avoiding this race. Test Plan: - Tried slow validate locally: this patch does not introduce new failures. - circleci: https://circleci.com/gh/ghc/ghc-diffs/283 The test got killed because it took 5 hours but T7919 (which was previously failing on circleci) passed. Reviewers: simonmar, bgamari, erikd Reviewed By: simonmar Subscribers: rwbarton, carter GHC Trac Issues: #15285 Differential Revision: https://phabricator.haskell.org/D5115 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11#comment:3> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #12: Function missing ?
by GHC 06 Sep '18

06 Sep '18

#12: Function missing ? --------------------------------+-------------------- Reporter: nobody | Owner: nobody Type: bug | Status: closed Priority: normal | Milestone: Component: hslibs/net | Version: 5.02 Resolution: Fixed | Keywords: Type of failure: None/Unknown | --------------------------------+-------------------- Changes (by Ömer Sinan Ağacan <omeragacan@…>): * failure: => None/Unknown Comment: In [changeset:"c6fbac6a6a69a2f4be89701b2c386ae53214f9a3/ghc" c6fbac6/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="c6fbac6a6a69a2f4be89701b2c386ae53214f9a3" Fix a race between GC threads in concurrent scavenging While debugging #15285 I realized that free block lists (free_list in BlockAlloc.c) get corrupted when multiple scavenge threads allocate and release blocks concurrently. Here's a picture of one such race: Thread 2 (Thread 32573.32601): #0 check_tail (bd=0x940d40 <stg_TSO_info>) at rts/sm/BlockAlloc.c:860 #1 0x0000000000928ef7 in checkFreeListSanity () at rts/sm/BlockAlloc.c:896 #2 0x0000000000928979 in freeGroup (p=0x7e998ce02880) at rts/sm/BlockAlloc.c:721 #3 0x0000000000928a17 in freeChain (bd=0x7e998ce02880) at rts/sm/BlockAlloc.c:738 #4 0x0000000000926911 in freeChain_sync (bd=0x7e998ce02880) at rts/sm/GCUtils.c:80 #5 0x0000000000934720 in scavenge_capability_mut_lists (cap=0x1acae80) at rts/sm/Scav.c:1665 #6 0x000000000092b411 in gcWorkerThread (cap=0x1acae80) at rts/sm/GC.c:1157 #7 0x000000000090be9a in yieldCapability (pCap=0x7f9994e69e20, task=0x7e9984000b70, gcAllowed=true) at rts/Capability.c:861 #8 0x0000000000906120 in scheduleYield (pcap=0x7f9994e69e50, task=0x7e9984000b70) at rts/Schedule.c:673 #9 0x0000000000905500 in schedule (initialCapability=0x1acae80, task=0x7e9984000b70) at rts/Schedule.c:293 #10 0x0000000000908d4f in scheduleWorker (cap=0x1acae80, task=0x7e9984000b70) at rts/Schedule.c:2554 #11 0x000000000091a30a in workerStart (task=0x7e9984000b70) at rts/Task.c:444 #12 0x00007f99937fa6db in start_thread (arg=0x7f9994e6a700) at pthread_create.c:463 #13 0x000061654d59f88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95 Thread 1 (Thread 32573.32573): #0 checkFreeListSanity () at rts/sm/BlockAlloc.c:887 #1 0x0000000000928979 in freeGroup (p=0x7e998d303540) at rts/sm/BlockAlloc.c:721 #2 0x0000000000926f23 in todo_block_full (size=513, ws=0x1aa8ce0) at rts/sm/GCUtils.c:264 #3 0x00000000009583b9 in alloc_for_copy (size=513, gen_no=0) at rts/sm/Evac.c:80 #4 0x000000000095850d in copy_tag_nolock (p=0x7e998c675f28, info=0x421d98 <Main_Large_con_info>, src=0x7e998d075d80, size=513, gen_no=0, tag=1) at rts/sm/Evac.c:153 #5 0x0000000000959177 in evacuate (p=0x7e998c675f28) at rts/sm/Evac.c:715 #6 0x0000000000932388 in scavenge_small_bitmap (p=0x7e998c675f28, size=1, bitmap=0) at rts/sm/Scav.c:271 #7 0x0000000000934aaf in scavenge_stack (p=0x7e998c675f28, stack_end=0x7e998c676000) at rts/sm/Scav.c:1908 #8 0x0000000000934295 in scavenge_one (p=0x7e998c66e000) at rts/sm/Scav.c:1466 #9 0x0000000000934662 in scavenge_mutable_list (bd=0x7e998d300440, gen=0x1b1d880) at rts/sm/Scav.c:1643 #10 0x0000000000934700 in scavenge_capability_mut_lists (cap=0x1aaa340) at rts/sm/Scav.c:1664 #11 0x00000000009299b6 in GarbageCollect (collect_gen=0, do_heap_census=false, gc_type=2, cap=0x1aaa340, idle_cap=0x1b38aa0) at rts/sm/GC.c:378 #12 0x0000000000907a4a in scheduleDoGC (pcap=0x7ffdec5b5310, task=0x1b36650, force_major=false) at rts/Schedule.c:1798 #13 0x0000000000905de7 in schedule (initialCapability=0x1aaa340, task=0x1b36650) at rts/Schedule.c:546 #14 0x0000000000908bc4 in scheduleWaitThread (tso=0x7e998c0067c8, ret=0x0, pcap=0x7ffdec5b5430) at rts/Schedule.c:2537 #15 0x000000000091b5a0 in rts_evalLazyIO (cap=0x7ffdec5b5430, p=0x9c11f0, ret=0x0) at rts/RtsAPI.c:530 #16 0x000000000091ca56 in hs_main (argc=1, argv=0x7ffdec5b5628, main_closure=0x9c11f0, rts_config=...) at rts/RtsMain.c:72 #17 0x0000000000421ea0 in main () In particular, dbl_link_onto() which is used to add a freed block to a doubly-linked free list is not thread safe and corrupts the list when called concurrently. Note that thread 1 is to blame here as thread 2 is properly taking the spinlock. With this patch we now take the spinlock when freeing a todo block in GC, avoiding this race. Test Plan: - Tried slow validate locally: this patch does not introduce new failures. - circleci: https://circleci.com/gh/ghc/ghc-diffs/283 The test got killed because it took 5 hours but T7919 (which was previously failing on circleci) passed. Reviewers: simonmar, bgamari, erikd Reviewed By: simonmar Subscribers: rwbarton, carter GHC Trac Issues: #15285 Differential Revision: https://phabricator.haskell.org/D5115 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12#comment:2> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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