From 3552ac862497bdb5ea73639851bbfd114b795fa2 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>

Date: Thu, 11 Mar 2021 20:41:36 +0100

Subject: [PATCH] Revert "sd-event: make use of epoll_pwait2() for greater time

 accuracy"

This reverts commit 798445ab84cff51bde7fcf936f0fb19c37cf858c.

Unfortunately this causes test-event to hang. 32 bit architectures seem

affected: i686 and arm32 in fedora koji. 32 bit build of test-event hangs

reliably under valgrind:

$ PKG_CONFIG_LIBDIR=/usr/lib/pkgconfig meson build-32 -Dc_args=-m32 -Dc_link_args=-m32 -Dcpp_args=-m32 -Dcpp_link_args=-m32 && ninja -C build-32 test-event && valgrind build/test-event

---

 src/libsystemd/sd-event/sd-event.c | 73 ++++++------------------------

 1 file changed, 14 insertions(+), 59 deletions(-)

diff --git a/src/libsystemd/sd-event/sd-event.c b/src/libsystemd/sd-event/sd-event.c

index 8ab9d419af..69d9c5e780 100644

--- a/src/libsystemd/sd-event/sd-event.c

+++ b/src/libsystemd/sd-event/sd-event.c

@@ -3781,59 +3781,9 @@ pending:

         return r;

 }

-static int epoll_wait_usec(

-                int fd,

-                struct epoll_event *events,

-                int maxevents,

-                usec_t timeout) {

-

-        static bool epoll_pwait2_absent = false;

-        int r, msec;

-

-        /* A wrapper that uses epoll_pwait2() if available, and falls back to epoll_wait() if not */

-

-        if (!epoll_pwait2_absent && timeout != USEC_INFINITY) {

-                struct timespec ts;

-

-                r = epoll_pwait2(fd,

-                                 events,

-                                 maxevents,

-                                 timespec_store(&ts, timeout),

-                                 NULL);

-                if (r >= 0)

-                        return r;

-                if (!ERRNO_IS_NOT_SUPPORTED(r) && !ERRNO_IS_PRIVILEGE(r))

-                        return -errno; /* Only fallback to old epoll_wait() if the syscall is masked or not

-                                        * supported. */

-

-                epoll_pwait2_absent = true;

-        }

-

-        if (timeout == USEC_INFINITY)

-                msec = -1;

-        else {

-                usec_t k;

-

-                k = DIV_ROUND_UP(timeout, USEC_PER_MSEC);

-                if (k >= INT_MAX)

-                        msec = INT_MAX; /* Saturate */

-                else

-                        msec = (int) k;

-        }

-

-        r = epoll_wait(fd,

-                       events,

-                       maxevents,

-                       msec);

-        if (r < 0)

-                return -errno;

-

-        return r;

-}

-

 _public_ int sd_event_wait(sd_event *e, uint64_t timeout) {

         size_t n_event_queue, m;

-        int r;

+        int r, msec;

         assert_return(e, -EINVAL);

         assert_return(e = event_resolve(e), -ENOPKG);

@@ -3852,16 +3802,21 @@ _public_ int sd_event_wait(sd_event *e, uint64_t timeout) {

         /* If we still have inotify data buffered, then query the other fds, but don't wait on it */

         if (e->inotify_data_buffered)

-                timeout = 0;

+                msec = 0;

+        else

+                msec = timeout == (uint64_t) -1 ? -1 : (int) DIV_ROUND_UP(timeout, USEC_PER_MSEC);

         for (;;) {

-                r = epoll_wait_usec(e->epoll_fd, e->event_queue, e->event_queue_allocated, timeout);

-                if (r == -EINTR) {

-                        e->state = SD_EVENT_PENDING;

-                        return 1;

-                }

-                if (r < 0)

+                r = epoll_wait(e->epoll_fd, e->event_queue, e->event_queue_allocated, msec);

+                if (r < 0) {

+                        if (errno == EINTR) {

+                                e->state = SD_EVENT_PENDING;

+                                return 1;

+                        }

+

+                        r = -errno;

                         goto finish;

+                }

                 m = (size_t) r;

@@ -3874,7 +3829,7 @@ _public_ int sd_event_wait(sd_event *e, uint64_t timeout) {

                 if (!GREEDY_REALLOC(e->event_queue, e->event_queue_allocated, e->event_queue_allocated + n_event_queue))

                         return -ENOMEM;

-                timeout = 0;

+                msec = 0;

         }

         triple_timestamp_get(&e->timestamp);

-- 

2.30.1