linux: make timerfd_settime(2) set expirations count to zero
On Linux, read(2) from a timerfd file descriptor returns an unsigned 8-byte integer (uint64_t) containing the number of expirations that have occurred, if the timer has already expired one or more times since its settings were last modified using timerfd_settime(), or since the last successful read(2). That's to say, once we do a read or call timerfd_settime(), timer fd's expiration count should be zero. Some Linux applications create timerfd and add it to epoll with LT mode, when event comes, they do timerfd_settime instead of read to stop event source from trigger. On FreeBSD, timerfd_settime(2) didn't set the count to zero, which caused high CPU utilization. Submitted by: ankohuu_outlook.com (Shunchao Hu) Differential Revision: https://reviews.freebsd.org/D28231
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@ -981,6 +981,7 @@ linux_timerfd_settime(struct thread *td, struct linux_timerfd_settime_args *args
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linux_timerfd_curval(tfd, &ots);
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tfd->tfd_time = nts;
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tfd->tfd_count = 0;
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if (timespecisset(&nts.it_value)) {
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linux_timerfd_clocktime(tfd, &cts);
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ts = nts.it_value;
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