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Revert "Address a race condition in libevent select." #7940

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Jul 28, 2020
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Revert "Address a race condition in libevent select." #7940

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29 changes: 5 additions & 24 deletions opal/mca/event/libevent2022/libevent/select.c
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Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,6 @@
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>

#include "event-internal.h"
#include "evsignal-internal.h"
Expand Down Expand Up @@ -167,30 +166,12 @@ select_dispatch(struct event_base *base, struct timeval *tv)
check_selectop(sop);

if (res == -1) {
if (errno == EINTR) {
return (0);
if (errno != EINTR) {
event_warn("select");
return (-1);
}
/* There seems to be a very subtle race condition between the
* event_del and the select, where the fd is still active on the
* event_readset_in but no libevent structure make reference
* to it so it. Thus, any call to progress will no nothing more
* than print a warning and do nothing, leading to deadlocks.
* If we force remove the problematic fd, we get the warning only
* once, and things work as expected.
*/
event_warn("select");
for (j = 0; j < nfds; ++j) {
if (FD_ISSET(j, sop->event_readset_in) ||
FD_ISSET(j, sop->event_writeset_in)) {
res = fcntl(j, F_GETFL);
if( res == -1 ) {
event_warn("bad file descriptor %d/%d\n", j, nfds);
FD_CLR(j, sop->event_readset_in);
FD_CLR(j, sop->event_writeset_in);
}
}
}
return (-1);

return (0);
}

event_debug(("%s: select reports %d", __func__, res));
Expand Down