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block signals during fork 

there are several reasons for this. some of them are related to race
conditions that arise since fork is required to be async-signal-safe:
if fork or pthread_create is called from a signal handler after the
fork syscall has returned but before the subsequent userspace code has
finished, inconsistent state could result. also, there seem to be
kernel and/or strace bugs related to arrival of signals during fork,
at least on some versions, and simply blocking signals eliminates the
possibility of such bugs.
This commit is contained in:
Rich Felker 2013-08-08 23:17:05 -04:00
parent 72482f9020
commit d4d6d6f322
1 changed files with 3 additions and 0 deletions
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3
src/process/fork.c
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@ -13,7 +13,9 @@ weak_alias(dummy, __fork_handler);
pid_t fork(void) pid_t fork(void)
{ {
pid_t ret; pid_t ret;
sigset_t set;
__fork_handler(-1); __fork_handler(-1);
__block_all_sigs(&set);
ret = syscall(SYS_fork); ret = syscall(SYS_fork);
if (libc.main_thread && !ret) { if (libc.main_thread && !ret) {
pthread_t self = __pthread_self(); pthread_t self = __pthread_self();
@ -22,6 +24,7 @@ pid_t fork(void)
libc.threads_minus_1 = 0; libc.threads_minus_1 = 0;
libc.main_thread = self; libc.main_thread = self;
} }
__restore_sigs(&set);
__fork_handler(!ret); __fork_handler(!ret);
return ret; return ret;
} }