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authorAndreas Voellmy <andreas.voellmy@gmail.com>2015-03-09 18:27:41 -0400
committerAndreas Voellmy <andreas.voellmy@gmail.com>2015-03-09 18:27:42 -0400
commit74625d6847e970e8bdc6991c327515b3e10b231b (patch)
treebae80afff917229456182cbe4b166ac458d560be /rts/posix/Signals.c
parente76f86646229b3f8bcdc6ad71d464104c639f431 (diff)
downloadhaskell-74625d6847e970e8bdc6991c327515b3e10b231b.tar.gz
RTS/IOManager: fix trac issue #9722.
Summary: Whenever the RTS has been inactive for idleGCDelayTime, the idle timer fires and calls wakeUpRts(), which in turn calls ioManagerWakeup(), which in turn writes a byte (or a few) to a file descriptor (stored in the io_manager_wakeup_fd variable) registered by the TimerManager and on which the TimerManager will wait. (Note that the write will only occur if the file descriptor is non-negative.) When the RTS shuts down, it shuts down the TimerManager, and in this process the file descriptor stored in io_manager_wakeup_fd is closed. In the error case, the idle timer fires after the close of the file occurs, and then the write() call in ioManagerWakeup() fails and the aforementioned error message gets printed. This patch solves the problem by (1) having the TimerManager (via Control) write -1 to io_manager_wakeup_fd just before closing the file descriptor written in io_manager_wakeup_fd, and (2) having ioManagerWakeup() ignore an error returned by write() in the case that the write returned -1 and the io_manager_wakeup_fd is -1. Reviewers: austin, simonmar, hvr, thomie Reviewed By: thomie Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D722 GHC Trac Issues: #9722
Diffstat (limited to 'rts/posix/Signals.c')
-rw-r--r--rts/posix/Signals.c17
1 files changed, 15 insertions, 2 deletions
diff --git a/rts/posix/Signals.c b/rts/posix/Signals.c
index 5fbb917cf8..a2fa07f091 100644
--- a/rts/posix/Signals.c
+++ b/rts/posix/Signals.c
@@ -126,7 +126,7 @@ more_handlers(int sig)
}
// Here's the pipe into which we will send our signals
-static int io_manager_wakeup_fd = -1;
+static volatile int io_manager_wakeup_fd = -1;
static int timer_manager_control_wr_fd = -1;
#define IO_MANAGER_WAKEUP 0xff
@@ -161,7 +161,20 @@ ioManagerWakeup (void)
StgWord8 byte = (StgWord8)IO_MANAGER_WAKEUP;
r = write(io_manager_wakeup_fd, &byte, 1);
#endif
- if (r == -1) { sysErrorBelch("ioManagerWakeup: write"); }
+ /* N.B. If the TimerManager is shutting down as we run this
+ * then there is a possiblity that our first read of
+ * io_manager_wakeup_fd is non-negative, but before we get to the
+ * write the file is closed. If this occurs, io_manager_wakeup_fd
+ * will be written into with -1 (GHC.Event.Control does this prior
+ * to closing), so checking this allows us to distinguish this case.
+ * To ensure we observe the correct ordering, we declare the
+ * io_manager_wakeup_fd as volatile.
+ * Since this is not an error condition, we do not print the error
+ * message in this case.
+ */
+ if (r == -1 && io_manager_wakeup_fd >= 0) {
+ sysErrorBelch("ioManagerWakeup: write");
+ }
}
}