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linux: fix epoll_pwait() regression with < 2.6.19

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Linux before kernel 2.6.19 does not support epoll_pwait().  Due to a
logic error in commit 2daf944 ("unix: add flag for blocking SIGPROF
during poll"), the fallback path for ENOSYS was not taken.

This commit also adds epoll_pwait() emulation using pthread_sigmask().
The block/unblock operations are not atomic but that is fine for our
particular use case, to wit, sleep through SIGPROF signals.

PR-URL: https://github.com/libuv/libuv/pull/162
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>
This commit is contained in:
Ben Noordhuis 2015-01-23 23:32:19 +01:00
parent f2bb8d394c
commit 67bb2b5f70
1 changed files with 25 additions and 6 deletions
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31
src/unix/linux-core.c
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@ -136,11 +136,14 @@ void uv__platform_invalidate_fd(uv_loop_t* loop, int fd) {
void uv__io_poll(uv_loop_t* loop, int timeout) {
static int no_epoll_pwait;
static int no_epoll_wait;
struct uv__epoll_event events[1024];
struct uv__epoll_event* pe;
struct uv__epoll_event e;
QUEUE* q;
uv__io_t* w;
sigset_t sigset;
uint64_t sigmask;
uint64_t base;
uint64_t diff;
@ -150,7 +153,6 @@ void uv__io_poll(uv_loop_t* loop, int timeout) {
int fd;
int op;
int i;
static int no_epoll_wait;
if (loop->nfds == 0) {
assert(QUEUE_EMPTY(&loop->watcher_queue));
@ -193,31 +195,42 @@ void uv__io_poll(uv_loop_t* loop, int timeout) {
}
sigmask = 0;
if (loop->flags & UV_LOOP_BLOCK_SIGPROF)
if (loop->flags & UV_LOOP_BLOCK_SIGPROF) {
sigemptyset(&sigset);
sigaddset(&sigset, SIGPROF);
sigmask |= 1 << (SIGPROF - 1);
}
assert(timeout >= -1);
base = loop->time;
count = 48; /* Benchmarks suggest this gives the best throughput. */
for (;;) {
if (no_epoll_wait || sigmask) {
if (sigmask != 0 && no_epoll_pwait != 0)
if (pthread_sigmask(SIG_BLOCK, &sigset, NULL))
abort();
if (sigmask != 0 && no_epoll_pwait == 0) {
nfds = uv__epoll_pwait(loop->backend_fd,
events,
ARRAY_SIZE(events),
timeout,
sigmask);
if (nfds == -1 && errno == ENOSYS)
no_epoll_pwait = 1;
} else {
nfds = uv__epoll_wait(loop->backend_fd,
events,
ARRAY_SIZE(events),
timeout);
if (nfds == -1 && errno == ENOSYS) {
if (nfds == -1 && errno == ENOSYS)
no_epoll_wait = 1;
continue;
}
}
if (sigmask != 0 && no_epoll_pwait != 0)
if (pthread_sigmask(SIG_UNBLOCK, &sigset, NULL))
abort();
/* Update loop->time unconditionally. It's tempting to skip the update when
* timeout == 0 (i.e. non-blocking poll) but there is no guarantee that the
* operating system didn't reschedule our process while in the syscall.
@ -230,6 +243,12 @@ void uv__io_poll(uv_loop_t* loop, int timeout) {
}
if (nfds == -1) {
if (errno == ENOSYS) {
/* epoll_wait() or epoll_pwait() failed, try the other system call. */
assert(no_epoll_wait == 0 || no_epoll_pwait == 0);
continue;
}
if (errno != EINTR)
abort();