Handling sys_futex EINTR allows us to retry waiting on the futex
immediately if we are interrupted by a signal without having to try
connecting to the session daemon.
This should not impact correctness though, as the wait scheme would
simply try to connect, fail, and try waiting again.
Also handle errors on FUTEX_WAKE.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
static
void wait_for_sessiond(struct sock_info *sock_info)
{
static
void wait_for_sessiond(struct sock_info *sock_info)
{
if (ust_lock()) {
goto quit;
}
if (ust_lock()) {
goto quit;
}
DBG("Waiting for %s apps sessiond", sock_info->name);
/* Wait for futex wakeup */
DBG("Waiting for %s apps sessiond", sock_info->name);
/* Wait for futex wakeup */
- if (uatomic_read((int32_t *) sock_info->wait_shm_mmap) == 0) {
- ret = futex_async((int32_t *) sock_info->wait_shm_mmap,
- FUTEX_WAIT, 0, NULL, NULL, 0);
- if (ret < 0) {
- if (errno == EFAULT) {
- wait_poll_fallback = 1;
- DBG(
+ if (uatomic_read((int32_t *) sock_info->wait_shm_mmap))
+ goto end_wait;
+
+ while (futex_async((int32_t *) sock_info->wait_shm_mmap,
+ FUTEX_WAIT, 0, NULL, NULL, 0)) {
+ switch (errno) {
+ case EWOULDBLOCK:
+ /* Value already changed. */
+ goto end_wait;
+ case EINTR:
+ /* Retry if interrupted by signal. */
+ break; /* Get out of switch. */
+ case EFAULT:
+ wait_poll_fallback = 1;
+ DBG(
"Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
"do not support FUTEX_WAKE on read-only memory mappings correctly. "
"Please upgrade your kernel "
"(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
"mainline). LTTng-UST will use polling mode fallback.");
"Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
"do not support FUTEX_WAKE on read-only memory mappings correctly. "
"Please upgrade your kernel "
"(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
"mainline). LTTng-UST will use polling mode fallback.");
- if (ust_debug())
- PERROR("futex");
- }
+ if (ust_debug())
+ PERROR("futex");
+ goto end_wait;
if (active) {
uatomic_set((int32_t *) wait_shm_mmap, 1);
if (active) {
uatomic_set((int32_t *) wait_shm_mmap, 1);
- futex_async((int32_t *) wait_shm_mmap, FUTEX_WAKE,
- INT_MAX, NULL, NULL, 0);
+ if (futex_async((int32_t *) wait_shm_mmap, FUTEX_WAKE,
+ INT_MAX, NULL, NULL, 0) < 0) {
+ perror("futex_async");
+ goto error;
+ }
} else {
uatomic_set((int32_t *) wait_shm_mmap, 0);
}
} else {
uatomic_set((int32_t *) wait_shm_mmap, 0);
}
if (active) {
uatomic_set((int32_t *) wait_shm_mmap, 1);
if (active) {
uatomic_set((int32_t *) wait_shm_mmap, 1);
- futex_async((int32_t *) wait_shm_mmap, FUTEX_WAKE,
- INT_MAX, NULL, NULL, 0);
+ if (futex_async((int32_t *) wait_shm_mmap, FUTEX_WAKE,
+ INT_MAX, NULL, NULL, 0) < 0) {
+ perror("futex_async");
+ goto error;
+ }
} else {
uatomic_set((int32_t *) wait_shm_mmap, 0);
}
} else {
uatomic_set((int32_t *) wait_shm_mmap, 0);
}