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MEDIUM: epoll: skip reports of stale file descriptors

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Now that we can see that some events are reported for older instances
of a file descriptor, let's skip these ones instead of reporting
dangerous events on them. It might possibly qualify as a bug if it
helps fixing strange issues in certain environments, in which case it
can make sense to backport it along with the following recent patches:

  DEBUG: fd: add a counter of takeovers of an FD since it was last opened
  MINOR: fd: add a generation number to file descriptors
  DEBUG: epoll: store and compare the FD's generation count with reported event
This commit is contained in:
Willy Tarreau 2025-01-30 16:32:35 +01:00
parent 5012b6c6d9
commit 8235a24782
1 changed files with 4 additions and 1 deletions
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5
src/ev_epoll.c
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@ -266,7 +266,9 @@ static void _do_poll(struct poller *p, int exp, int wake)
fd_gen = _HA_ATOMIC_LOAD(&fdtab[fd].generation); fd_gen = _HA_ATOMIC_LOAD(&fdtab[fd].generation);
if (unlikely(ev_gen != fd_gen)) { if (unlikely(ev_gen != fd_gen)) {
/* this is a stale report for an older instance of this FD */ /* this is a stale report for an older instance of this FD,
* we must ignore it.
*/
if (_HA_ATOMIC_LOAD(&fdtab[fd].owner)) { if (_HA_ATOMIC_LOAD(&fdtab[fd].owner)) {
ulong tmask = _HA_ATOMIC_LOAD(&fdtab[fd].thread_mask); ulong tmask = _HA_ATOMIC_LOAD(&fdtab[fd].thread_mask);
@ -297,6 +299,7 @@ static void _do_poll(struct poller *p, int exp, int wake)
} else { } else {
COUNT_IF(1, "epoll report of event on a just closed fd (harmless)"); COUNT_IF(1, "epoll report of event on a just closed fd (harmless)");
} }
continue;
} }
if ((e & EPOLLRDHUP) && !(cur_poller.flags & HAP_POLL_F_RDHUP)) if ((e & EPOLLRDHUP) && !(cur_poller.flags & HAP_POLL_F_RDHUP))