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Make forking off threads reliable on Windows

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This change makes posix_spawn_test no longer flaky on Windows, by (1)
fixing a race condition in wait(), and (2) removing a misguided vfork
implementation which was letting Windows bypass pthread_atfork().
This commit is contained in:
Justine Tunney 2023-07-30 08:55:01 -07:00
parent 2ebc5781a1
commit 58352df0a4
No known key found for this signature in database
GPG key ID: BE714B4575D6E328
30 changed files with 230 additions and 187 deletions
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30
libc/calls/__sig2.c
View file

@ -19,6 +19,7 @@
#include "ape/sections.internal.h"
#include "libc/assert.h"
#include "libc/calls/calls.h"
#include "libc/calls/internal.h"
#include "libc/calls/sig.internal.h"
#include "libc/calls/state.internal.h"
#include "libc/calls/struct/sigaction.h"
@ -75,12 +76,14 @@ textwindows int __sig_is_applicable(struct Signal *s) {
* Dequeues signal that isn't masked.
* @return signal or null if empty or none unmasked
*/
static textwindows struct Signal *__sig_remove(void) {
static textwindows struct Signal *__sig_remove(int sigops) {
struct Signal *prev, *res;
if (__sig.queue) {
__sig_lock();
for (prev = 0, res = __sig.queue; res; prev = res, res = res->next) {
if (__sig_is_applicable(res) && !__sig_is_masked(res->sig)) {
if (__sig_is_applicable(res) && //
!__sig_is_masked(res->sig) && //
!((sigops & kSigOpNochld) && res->sig == SIGCHLD)) {
if (res == __sig.queue) {
__sig.queue = res->next;
} else if (prev) {
@ -102,8 +105,7 @@ static textwindows struct Signal *__sig_remove(void) {
* @note called from main thread
* @return true if EINTR should be returned by caller
*/
static bool __sig_deliver(bool restartable, int sig, int si_code,
ucontext_t *ctx) {
static bool __sig_deliver(int sigops, int sig, int si_code, ucontext_t *ctx) {
unsigned rva, flags;
siginfo_t info, *infop;
STRACE("delivering %G", sig);
@ -145,7 +147,7 @@ static bool __sig_deliver(bool restartable, int sig, int si_code,
}
}
if (!restartable) {
if (!(sigops & kSigOpRestartable)) {
return true; // always send EINTR for wait4(), poll(), etc.
} else if (flags & SA_RESTART) {
STRACE("restarting syscall on %G", sig);
@ -168,11 +170,9 @@ static textwindows bool __sig_is_fatal(int sig) {
/**
* Handles signal.
*
* @param restartable can be used to suppress true return if SA_RESTART
* @return true if signal was delivered
*/
bool __sig_handle(bool restartable, int sig, int si_code, ucontext_t *ctx) {
bool __sig_handle(int sigops, int sig, int si_code, ucontext_t *ctx) {
bool delivered;
switch (__sighandrvas[sig]) {
case (intptr_t)SIG_DFL:
@ -186,7 +186,7 @@ bool __sig_handle(bool restartable, int sig, int si_code, ucontext_t *ctx) {
delivered = false;
break;
default:
delivered = __sig_deliver(restartable, sig, si_code, ctx);
delivered = __sig_deliver(sigops, sig, si_code, ctx);
break;
}
return delivered;
@ -226,7 +226,9 @@ textwindows int __sig_add(int tid, int sig, int si_code) {
int rc;
struct Signal *mem;
if (1 <= sig && sig <= 64) {
if (__sighandrvas[sig] == (unsigned)(intptr_t)SIG_IGN) {
if (__sighandrvas[sig] == (unsigned)(uintptr_t)SIG_IGN ||
(__sighandrvas[sig] == (unsigned)(uintptr_t)SIG_DFL &&
!__sig_is_fatal(sig))) {
STRACE("ignoring %G", sig);
rc = 0;
} else {
@ -253,19 +255,17 @@ textwindows int __sig_add(int tid, int sig, int si_code) {
/**
* Checks for unblocked signals and delivers them on New Technology.
*
* @param restartable is for functions like read() but not poll()
* @return true if EINTR should be returned by caller
* @note called from main thread
* @threadsafe
*/
textwindows bool __sig_check(bool restartable) {
textwindows bool __sig_check(int sigops) {
unsigned rva;
bool delivered;
struct Signal *sig;
delivered = false;
while ((sig = __sig_remove())) {
delivered |= __sig_handle(restartable, sig->sig, sig->si_code, 0);
while ((sig = __sig_remove(sigops))) {
delivered |= __sig_handle(sigops, sig->sig, sig->si_code, 0);
__sig_free(sig);
}
return delivered;