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add pending state back to jl_thread_suspend_and_get_state-machine #55622

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Aug 29, 2024
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add pending state back to jl_thread_suspend_and_get_state-machine #55622

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65 changes: 55 additions & 10 deletions src/signals-unix.c
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Original file line number Diff line number Diff line change
Expand Up @@ -448,6 +448,7 @@ static int signal_caught_cond = -1;

int jl_thread_suspend_and_get_state(int tid, int timeout, bt_context_t *ctx)
{
int err;
pthread_mutex_lock(&in_signal_lock);
jl_ptls_t ptls2 = jl_atomic_load_relaxed(&jl_all_tls_states)[tid];
jl_task_t *ct2 = ptls2 ? jl_atomic_load_relaxed(&ptls2->current_task) : NULL;
Expand All @@ -456,22 +457,51 @@ int jl_thread_suspend_and_get_state(int tid, int timeout, bt_context_t *ctx)
pthread_mutex_unlock(&in_signal_lock);
return 0;
}
sig_atomic_t request = 0;
if (!jl_atomic_cmpswap(&ptls2->signal_request, &request, 1)) {
if (jl_atomic_load(&ptls2->signal_request) != 0) {
// something is wrong, or there is already a usr2 in flight elsewhere
// try to wait for it to finish or wait for timeout
struct pollfd event = {signal_caught_cond, POLLIN, 0};
do {
err = poll(&event, 1, timeout * 1000);
} while (err == -1 && errno == EINTR);
if (err == -1 || (event.revents & POLLIN) == 0) {
// not ready after timeout: cancel this request
pthread_mutex_unlock(&in_signal_lock);
return 0;
}
}
// check for any stale signal_caught_cond events
struct pollfd event = {signal_caught_cond, POLLIN, 0};
do {
err = poll(&event, 1, 0);
} while (err == -1 && errno == EINTR);
if (err == -1) {
pthread_mutex_unlock(&in_signal_lock);
return 0;
}
if ((event.revents & POLLIN) != 0) {
// consume it before continuing
eventfd_t got;
do {
err = read(signal_caught_cond, &got, sizeof(eventfd_t));
} while (err == -1 && errno == EINTR);
if (err != sizeof(eventfd_t)) abort();
assert(got == 1); (void) got;
}
sig_atomic_t request = jl_atomic_exchange(&ptls2->signal_request, 1);
assert(request == 0 || request == -1);
request = 1;
int err = pthread_kill(ptls2->system_id, SIGUSR2);
// wait for thread to acknowledge or timeout
struct pollfd event = {signal_caught_cond, POLLIN, 0};
err = pthread_kill(ptls2->system_id, SIGUSR2);
if (err == 0) {
// wait for thread to acknowledge or timeout
struct pollfd event = {signal_caught_cond, POLLIN, 0};
do {
err = poll(&event, 1, timeout * 1000);
} while (err == -1 && errno == EINTR);
if (err != 1 || (event.revents & POLLIN) == 0)
err = -1;
}
if ((event.revents & POLLIN) == 0) {
if (err == -1) {
// not ready after timeout: try to cancel this request
if (jl_atomic_cmpswap(&ptls2->signal_request, &request, 0)) {
pthread_mutex_unlock(&in_signal_lock);
Expand All @@ -487,7 +517,7 @@ int jl_thread_suspend_and_get_state(int tid, int timeout, bt_context_t *ctx)
// Now the other thread is waiting on exit_signal_cond (verify that here by
// checking it is 0, and add an acquire barrier for good measure)
request = jl_atomic_load_acquire(&ptls2->signal_request);
assert(request == 0); (void) request;
assert(request == 0 || request == -1); (void) request;
jl_atomic_store_release(&ptls2->signal_request, 4); // prepare to resume normally, but later code may change this
*ctx = *signal_context;
return 1;
Expand Down Expand Up @@ -546,6 +576,7 @@ static void jl_exit_thread0(int signo, jl_bt_element_t *bt_data, size_t bt_size)
}

// request:
// -1: processing
// 0: nothing [not from here]
// 1: get state & wait for request
// 2: throw sigint if `!defer_signal && io_wait` or if force throw threshold
Expand All @@ -561,22 +592,36 @@ void usr2_handler(int sig, siginfo_t *info, void *ctx)
if (ptls == NULL)
return;
int errno_save = errno;
// acknowledge that we saw the signal_request
sig_atomic_t request = jl_atomic_exchange(&ptls->signal_request, 0);
sig_atomic_t request = jl_atomic_load(&ptls->signal_request);
if (request == 0)
return;
if (!jl_atomic_cmpswap(&ptls->signal_request, &request, -1))
return;
if (request == 1) {
signal_context = jl_to_bt_context(ctx);
// acknowledge that we saw the signal_request and set signal_context
int err;
eventfd_t got = 1;
err = write(signal_caught_cond, &got, sizeof(eventfd_t));
if (err != sizeof(eventfd_t)) abort();
sig_atomic_t processing = -1;
jl_atomic_cmpswap(&ptls->signal_request, &processing, 0);
// wait for exit signal
do {
err = read(exit_signal_cond, &got, sizeof(eventfd_t));
} while (err == -1 && errno == EINTR);
if (err != sizeof(eventfd_t)) abort();
assert(got == 1);
request = jl_atomic_exchange(&ptls->signal_request, 0);
request = jl_atomic_exchange(&ptls->signal_request, -1);
signal_context = NULL;
assert(request == 2 || request == 3 || request == 4);
}
int err;
eventfd_t got = 1;
err = write(signal_caught_cond, &got, sizeof(eventfd_t));
if (err != sizeof(eventfd_t)) abort();
sig_atomic_t processing = -1;
jl_atomic_cmpswap(&ptls->signal_request, &processing, 0);
if (request == 2) {
int force = jl_check_force_sigint();
if (force || (!ptls->defer_signal && ptls->io_wait)) {
Expand Down