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authorJeff King <peff@peff.net>2016-02-24 02:40:16 -0500
committerJunio C Hamano <gitster@pobox.com>2016-02-25 13:51:45 -0800
commit9658846ce3d379b9ff8010a2ed326fcafc10eb82 (patch)
tree815ab2d39efc3f4f591861dd43f050e5913a794e
parent326e5bc91eecf73234ead29636207bc516573e79 (diff)
downloadgit-9658846ce3d379b9ff8010a2ed326fcafc10eb82.tar.gz
write_or_die: handle EPIPE in async threads
When write_or_die() sees EPIPE, it treats it specially by converting it into a SIGPIPE death. We obviously cannot ignore it, as the write has failed and the caller expects us to die. But likewise, we cannot just call die(), because printing any message at all would be a nuisance during normal operations. However, this is a problem if write_or_die() is called from a thread. Our raised signal ends up killing the whole process, when logically we just need to kill the thread (after all, if we are ignoring SIGPIPE, there is good reason to think that the main thread is expecting to handle it). Inside an async thread, the die() code already does the right thing, because we use our custom die_async() routine, which calls pthread_join(). So ideally we would piggy-back on that, and simply call: die_quietly_with_code(141); or similar. But refactoring the die code to do this is surprisingly non-trivial. The die_routines themselves handle both printing and the decision of the exit code. Every one of them would have to be modified to take new parameters for the code, and to tell us to be quiet. Instead, we can just teach write_or_die() to check for the async case and handle it specially. We do have to build an interface to abstract the async exit, but it's simple and self-contained. If we had many call-sites that wanted to do this die_quietly_with_code(), this approach wouldn't scale as well, but we don't. This is the only place where do this weird exit trick. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
-rw-r--r--run-command.c10
-rw-r--r--run-command.h1
-rw-r--r--write_or_die.c4
3 files changed, 15 insertions, 0 deletions
diff --git a/run-command.c b/run-command.c
index 13fa452e8c..3add1d66ac 100644
--- a/run-command.c
+++ b/run-command.c
@@ -633,6 +633,11 @@ int in_async(void)
return !pthread_equal(main_thread, pthread_self());
}
+void NORETURN async_exit(int code)
+{
+ pthread_exit((void *)(intptr_t)code);
+}
+
#else
static struct {
@@ -678,6 +683,11 @@ int in_async(void)
return process_is_async;
}
+void NORETURN async_exit(int code)
+{
+ exit(code);
+}
+
#endif
int start_async(struct async *async)
diff --git a/run-command.h b/run-command.h
index 12bb26c2a6..c0969c7695 100644
--- a/run-command.h
+++ b/run-command.h
@@ -121,5 +121,6 @@ struct async {
int start_async(struct async *async);
int finish_async(struct async *async);
int in_async(void);
+void NORETURN async_exit(int code);
#endif
diff --git a/write_or_die.c b/write_or_die.c
index e7afe7a295..49e80aa222 100644
--- a/write_or_die.c
+++ b/write_or_die.c
@@ -1,8 +1,12 @@
#include "cache.h"
+#include "run-command.h"
static void check_pipe(int err)
{
if (err == EPIPE) {
+ if (in_async())
+ async_exit(141);
+
signal(SIGPIPE, SIG_DFL);
raise(SIGPIPE);
/* Should never happen, but just in case... */