[commit: ghc] ghc-7.10: fix EBADF unqueueing in select backend (Trac #10590) (d3a2843)
git at git.haskell.org
git at git.haskell.org
Tue Sep 29 16:09:54 UTC 2015
Repository : ssh://git@git.haskell.org/ghc
On branch : ghc-7.10
Link : http://ghc.haskell.org/trac/ghc/changeset/d3a28430d89b256974ce09739f298ec68aa57a69/ghc
>---------------------------------------------------------------
commit d3a28430d89b256974ce09739f298ec68aa57a69
Author: Sergei Trofimovich <slyfox at gentoo.org>
Date: Tue Jul 7 17:00:23 2015 +0200
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 at 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
>---------------------------------------------------------------
d3a28430d89b256974ce09739f298ec68aa57a69
rts/RaiseAsync.c | 8 +-------
rts/RaiseAsync.h | 6 ++++++
rts/posix/Select.c | 10 ++++++++--
testsuite/tests/rts/T10590.hs | 37 +++++++++++++++++++++++++++++++++++++
testsuite/tests/rts/all.T | 5 +++++
5 files changed, 57 insertions(+), 9 deletions(-)
diff --git a/rts/RaiseAsync.c b/rts/RaiseAsync.c
index 3b206ff..267707c 100644
--- a/rts/RaiseAsync.c
+++ b/rts/RaiseAsync.c
@@ -23,12 +23,6 @@
#include "win32/IOManager.h"
#endif
-static StgTSO* raiseAsync (Capability *cap,
- StgTSO *tso,
- StgClosure *exception,
- rtsBool stop_at_atomically,
- StgUpdateFrame *stop_here);
-
static void removeFromQueues(Capability *cap, StgTSO *tso);
static void removeFromMVarBlockedQueue (StgTSO *tso);
@@ -777,7 +771,7 @@ removeFromQueues(Capability *cap, StgTSO *tso)
*
* -------------------------------------------------------------------------- */
-static StgTSO *
+StgTSO *
raiseAsync(Capability *cap, StgTSO *tso, StgClosure *exception,
rtsBool stop_at_atomically, StgUpdateFrame *stop_here)
{
diff --git a/rts/RaiseAsync.h b/rts/RaiseAsync.h
index 6bfed8d..1f939d4 100644
--- a/rts/RaiseAsync.h
+++ b/rts/RaiseAsync.h
@@ -19,6 +19,12 @@
void blockedThrowTo (Capability *cap,
StgTSO *target, MessageThrowTo *msg);
+StgTSO* raiseAsync (Capability *cap,
+ StgTSO *tso,
+ StgClosure *exception,
+ rtsBool stop_at_atomically,
+ StgUpdateFrame *stop_here);
+
void throwToSingleThreaded (Capability *cap,
StgTSO *tso,
StgClosure *exception);
diff --git a/rts/posix/Select.c b/rts/posix/Select.c
index 4b19235..d5c9b55 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,
diff --git a/testsuite/tests/rts/T10590.hs b/testsuite/tests/rts/T10590.hs
new file mode 100644
index 0000000..24198ab
--- /dev/null
+++ b/testsuite/tests/rts/T10590.hs
@@ -0,0 +1,37 @@
+import Foreign.C
+import Foreign.Marshal.Array
+import Foreign.Storable
+import Control.Concurrent
+
+-- The test works only on UNIX like.
+-- unportable bits:
+import qualified System.Posix.Internals as SPI
+import qualified System.Posix.Types as SPT
+
+pipe :: IO (CInt, CInt)
+pipe = allocaArray 2 $ \fds -> do
+ throwErrnoIfMinus1_ "pipe" $ SPI.c_pipe fds
+ rd <- peekElemOff fds 0
+ wr <- peekElemOff fds 1
+ return (rd, wr)
+
+main :: IO ()
+main = do
+ (r1, w1) <- pipe
+ (r2, _w2) <- pipe
+ _ <- forkIO $ do -- thread A
+ threadWaitRead (SPT.Fd r1)
+ _ <- forkIO $ do -- thread B
+ threadWaitRead (SPT.Fd r2)
+ yield -- switch to A, then B
+ -- now both are blocked
+ _ <- SPI.c_close w1 -- unblocking thread A fd
+ _ <- SPI.c_close r2 -- breaking thread B fd
+ yield -- kick RTS IO manager
+
+{-
+ Trac #10590 exposed a bug as:
+ T10590: internal error: removeThreadFromDeQueue: not found
+ (GHC version 7.11.20150702 for x86_64_unknown_linux)
+ Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
+ -}
diff --git a/testsuite/tests/rts/all.T b/testsuite/tests/rts/all.T
index 8e0e76e..e3b9da1 100644
--- a/testsuite/tests/rts/all.T
+++ b/testsuite/tests/rts/all.T
@@ -279,3 +279,8 @@ test('linker_error3',
ignore_output ],
run_command,
['$MAKE -s --no-print-directory linker_error3'])
+
+# ignore_output as RTS reports slightly different error messages
+# in 'epoll' and 'select' backends on reading from EBADF
+# mingw32 skip as UNIX pipe and close(fd) is used to exercise the problem
+test('T10590', [ignore_output, when(opsys('mingw32'),skip)], compile_and_run, [''])
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