Date: Mon, 7 Jun 2010 12:00:55 GMT From: Martin Simmons <martin@lispworks.com> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/147647: select wakes after 24 hours even if timeout is longer Message-ID: <201006071200.o57C0tcF097821@www.freebsd.org> Resent-Message-ID: <201006071210.o57CA3FR065013@freefall.freebsd.org>
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>Number: 147647 >Category: kern >Synopsis: select wakes after 24 hours even if timeout is longer >Confidential: no >Severity: non-critical >Priority: low >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Mon Jun 07 12:10:03 UTC 2010 >Closed-Date: >Last-Modified: >Originator: Martin Simmons >Release: 8.0-RELEASE-p2 >Organization: >Environment: FreeBSD lwfs1-cam.cam.lispworks.com 8.0-RELEASE-p2 FreeBSD 8.0-RELEASE-p2 #0: Tue Jan 5 21:11:58 UTC 2010 root@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64 >Description: The select system call wakes indicating timeout after 24 hours even if the timeout specifies a longer delay. >How-To-Repeat: Running the code below with argument 10000000 exits after 24 hours with: res = 0 delay = 86398 fd = 3, fd active = 0 #include <sys/select.h> #include <unistd.h> #include <time.h> #include <stdio.h> #include <stdlib.h> int main(int argc, char **argv) { fd_set fdset; struct timeval tv; int fds[2], fd, res; time_t start, end; pipe(fds); fd = fds[0]; tv.tv_sec = atoi(argv[1]); tv.tv_usec = 0; FD_ZERO(&fdset); FD_SET(fd, &fdset); start = time(NULL); res = select(fd + 1, &fdset, NULL, NULL, &tv); end = time(NULL); printf("res = %d delay = %ld fd = %d, fd active = %d\n", res, (long)(end - start), fd, FD_ISSET(fd, &fdset)); return 0; } >Fix: I think the problem is that seltdwait is implemented using cv_timedwait_sig, which returns EWOULDBLOCK on timeout. The calls to seltdwait in kern_select etc limit the timeout to a maximum of 24 * 60 * 60 * hz but interpret EWOULDBLOCK as a reason to exit rather than checking the actual timeout. >Release-Note: >Audit-Trail: >Unformatted:
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