From 507d7804c0b094889cd20f23ad9a48e2b76791f3 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Fri, 4 Sep 2015 11:35:57 +0200 Subject: pager: don't use unsafe functions in signal handlers Since the commit a3da8821208d (pager: do wait_for_pager on signal death), we call wait_for_pager() in the pager's signal handler. The recent bug report revealed that this causes a deadlock in glibc at aborting "git log" [*1*]. When this happens, git process is left unterminated, and it can't be killed by SIGTERM but only by SIGKILL. The problem is that wait_for_pager() function does more than waiting for pager process's termination, but it does cleanups and printing errors. Unfortunately, the functions that may be used in a signal handler are very limited [*2*]. Particularly, malloc(), free() and the variants can't be used in a signal handler because they take a mutex internally in glibc. This was the cause of the deadlock above. Other than the direct calls of malloc/free, many functions calling malloc/free can't be used. strerror() is such one, either. Also the usage of fflush() and printf() in a signal handler is bad, although it seems working so far. In a safer side, we should avoid them, too. This patch tries to reduce the calls of such functions in signal handlers. wait_for_signal() takes a flag and avoids the unsafe calls. Also, finish_command_in_signal() is introduced for the same reason. There the free() calls are removed, and only waits for the children without whining at errors. [*1*] https://bugzilla.opensuse.org/show_bug.cgi?id=942297 [*2*] http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04_03 Signed-off-by: Takashi Iwai Reviewed-by: Jeff King Signed-off-by: Junio C Hamano --- run-command.h | 1 + 1 file changed, 1 insertion(+) (limited to 'run-command.h') diff --git a/run-command.h b/run-command.h index 1103805af..518663eef 100644 --- a/run-command.h +++ b/run-command.h @@ -50,6 +50,7 @@ void child_process_init(struct child_process *); int start_command(struct child_process *); int finish_command(struct child_process *); +int finish_command_in_signal(struct child_process *); int run_command(struct child_process *); extern const char *find_hook(const char *name); -- cgit v1.2.1