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linux: Add clone3 CLONE_CLEAR_SIGHAND optimization to posix_spawn

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The clone3 flag resets all signal handlers of the child not set to
SIG_IGN to SIG_DFL.  It allows to skip most of the sigaction calls
to setup child signal handling, where previously a posix_spawn
had to issue 2 times NSIG sigaction calls (one to obtain the current
disposition and another to set either SIG_DFL or SIG_IGN).

With POSIX_SPAWN_SETSIGDEF the child will setup the signal for the case
where the disposition is SIG_IGN.

The code must handle the fallback where clone3 is not available. This is
done by splitting __clone_internal_fallback from __clone_internal.

Checked on x86_64-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
Adhemerval Zanella Netto
2023-01-12 10:58:51 -03:00
committed by Adhemerval Zanella
parent 2290cf73cc
commit 2053c11331
7 changed files with 238 additions and 27 deletions
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37
sysdeps/unix/sysv/linux/clone-internal.c
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@ -44,27 +44,15 @@ _Static_assert (sizeof (struct clone_args) == CLONE_ARGS_SIZE_VER2,
"sizeof (struct clone_args) != CLONE_ARGS_SIZE_VER2");
int
__clone_internal (struct clone_args *cl_args,
int (*func) (void *arg), void *arg)
__clone_internal_fallback (struct clone_args *cl_args,
int (*func) (void *arg), void *arg)
{
int ret;
#ifdef HAVE_CLONE3_WRAPPER
/* Try clone3 first. */
int saved_errno = errno;
ret = __clone3 (cl_args, sizeof (*cl_args), func, arg);
if (ret != -1 || errno != ENOSYS)
return ret;
/* NB: Restore errno since errno may be checked against non-zero
return value. */
__set_errno (saved_errno);
#endif
/* Map clone3 arguments to clone arguments. NB: No need to check
invalid clone3 specific bits in flags nor exit_signal since this
is an internal function. */
int flags = cl_args->flags | cl_args->exit_signal;
void *stack = cast_to_pointer (cl_args->stack);
int ret;
#ifdef __ia64__
ret = __clone2 (func, stack, cl_args->stack_size,
@ -88,4 +76,23 @@ __clone_internal (struct clone_args *cl_args,
return ret;
}
int
__clone_internal (struct clone_args *cl_args,
int (*func) (void *arg), void *arg)
{
#ifdef HAVE_CLONE3_WRAPPER
int saved_errno = errno;
int ret = __clone3 (cl_args, sizeof (*cl_args), func, arg);
if (ret != -1 || errno != ENOSYS)
return ret;
/* NB: Restore errno since errno may be checked against non-zero
return value. */
__set_errno (saved_errno);
#endif
return __clone_internal_fallback (cl_args, func, arg);
}
libc_hidden_def (__clone_internal)