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linux: handle EPOLLHUP without EPOLLIN/EPOLLOUT

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Work around an epoll quirk where it sometimes reports just the EPOLLERR
or EPOLLHUP event.  In order to force the event loop to move forward,
we merge in the read/write events that the watcher is interested in;
uv__read() and uv__write() will then deal with the error or hangup in
the usual fashion.

Fixes #982.

This is a back-port of commit 24bfef2 from the master branch.
This commit is contained in:
Ben Noordhuis 2013-11-08 05:10:44 +01:00
parent 991409e461
commit 0c76cdb98f
1 changed files with 25 additions and 7 deletions
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32
src/unix/linux-core.c
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@ -105,7 +105,6 @@ void uv__io_poll(uv_loop_t* loop, int timeout) {
uv__io_t* w;
uint64_t base;
uint64_t diff;
unsigned int masked_events;
int nevents;
int count;
int nfds;
@ -209,16 +208,35 @@ void uv__io_poll(uv_loop_t* loop, int timeout) {
continue;
}
/*
* Give users only events they're interested in. Prevents spurious
/* Give users only events they're interested in. Prevents spurious
* callbacks when previous callback invocation in this loop has stopped
* the current watcher. Also, filters out events that users has not
* requested us to watch.
*/
masked_events = pe->events & w->pevents;
if (masked_events != 0)
w->cb(loop, w, masked_events);
nevents++;
pe->events &= w->pevents | UV__POLLERR | UV__POLLHUP;
/* Work around an epoll quirk where it sometimes reports just the
* EPOLLERR or EPOLLHUP event. In order to force the event loop to
* move forward, we merge in the read/write events that the watcher
* is interested in; uv__read() and uv__write() will then deal with
* the error or hangup in the usual fashion.
*
* Note to self: happens when epoll reports EPOLLIN|EPOLLHUP, the user
* reads the available data, calls uv_read_stop(), then sometime later
* calls uv_read_start() again. By then, libuv has forgotten about the
* hangup and the kernel won't report EPOLLIN again because there's
* nothing left to read. If anything, libuv is to blame here. The
* current hack is just a quick bandaid; to properly fix it, libuv
* needs to remember the error/hangup event. We should get that for
* free when we switch over to edge-triggered I/O.
*/
if (pe->events == UV__EPOLLERR || pe->events == UV__EPOLLHUP)
pe->events |= w->pevents & (UV__EPOLLIN | UV__EPOLLOUT);
if (pe->events != 0) {
w->cb(loop, w, pe->events);
nevents++;
}
}
if (nevents != 0) {