Date: Wed, 16 Sep 2015 22:54:32 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 203162] when close(fd) on a fifo fails with EINTR, the file descriptor is not really closed Message-ID: <bug-203162-8-aT6ztCmnfA@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-203162-8@https.bugs.freebsd.org/bugzilla/> References: <bug-203162-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=203162 --- Comment #2 from Victor Stinner <victor.stinner@gmail.com> --- Created attachment 161127 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=161127&action=edit Syscalls seen by "truss -f" when the bug occurs Syscalls seen by "truss -f" when the bug occurs. Attached syscalls.txt is this command as a file, just if my comment is badly formatted in Bugzilla. parent = 57517 child = 61173 57517: open("(null)",O_WRONLY,037777777777) ERR#4 'Interrupted system call' 57517: SIGNAL 14 (SIGALRM) 57517: sigreturn(0x7fffffffe080,0x10006,0x7fffffffe080,0x0,0xffff80000060386e,0x0) ERR#4 'Interrupted system call' => parent is blocked on open(fifo, O_WRONLY) because the child didn't open it yet, but the open() is interrupted by signals every 10 ms. 61173: nanosleep({0.009149571 }) = 0 (0x0) 61173: SIGNAL 14 (SIGALRM) 61173: sigreturn(0x7fffffffe040,0x10006,0x7fffffffe040,0x1ff3019bb4b18,0xffffffff8093b550,0xfffff8001fcf9980) ERR#4 'Interrupted system call' => child is sleeping, nanosleep() is interrupted every 10 ms by a signal 57517: open("(null)",O_WRONLY,037777777777) = 0 (0x0) => strange, truss says that the parent succeeded first to open a FIFO to writing, whereas the child didn't open it yet. It looks more like a bug or race condition in truss. I prefer to think that the parent syscall succeeded after the open() in the child process. => moreover, no, the parent failed to open the FIFO: see below, it still tries to open it!? => And what is this strange file descriptor 0? It is supposed to be already be used by stdin... 61173: open("fifo_57517_465",O_RDONLY,042716203) = 4 (0x4) => child process opened the FIFO for reading, it should unblock open() in the parent. 61173: close(4) ERR#4 'Interrupted system call' => oh oh, closing the FIFO in the child process failed with EINTR... Bad things happens since this point. 57517: SIGNAL 14 (SIGALRM) 57517: sigreturn(0x7fffffffe080,0x10006,0x7fffffffe080,0x0,0xffff80000060386e,0x0) = 0 (0x0) => open() succeeded or was interrupted by EINTR? 61173: fstat(4,0x7fffffffe660) ERR#9 'Bad file descriptor' => fstat() confirms that the FIFO file descriptor is really closed in the child. 61173: setitimer(0,{0.000000, 0.000000 },0x0) = 0 (0x0) 61173: close(3) = 0 (0x0) => fd 3 is only used to workaround truss bugs, it's a copy of the stdout (fd 1). 61173: sigprocmask(SIG_BLOCK,SIGHUP|SIGINT|SIGQUIT|SIGKILL|SIGPIPE|SIGALRM|SIGTERM|SIGURG|SIGSTOP|SIGTSTP|SIGCONT|SIGCHLD|SIGTTIN|SIGTTOU|SIGIO|SIGXCPU|SIGXFSZ|SIGVTALRM|SIGPROF|SIGWINCH|SIGINFO|SIGUSR1|SIGUSR2,0x0) = 0 (0x0) 61173: sigprocmask(SIG_SETMASK,0x0,0x0) = 0 (0x0) 61173: sigprocmask(SIG_BLOCK,SIGHUP|SIGINT|SIGQUIT|SIGKILL|SIGPIPE|SIGALRM|SIGTERM|SIGURG|SIGSTOP|SIGTSTP|SIGCONT|SIGCHLD|SIGTTIN|SIGTTOU|SIGIO|SIGXCPU|SIGXFSZ|SIGVTALRM|SIGPROF|SIGWINCH|SIGINFO|SIGUSR1|SIGUSR2,0x0) = 0 (0x0) 61173: sigprocmask(SIG_SETMASK,0x0,0x0) = 0 (0x0) 61173: sigprocmask(SIG_BLOCK,SIGHUP|SIGINT|SIGQUIT|SIGKILL|SIGPIPE|SIGALRM|SIGTERM|SIGURG|SIGSTOP|SIGTSTP|SIGCONT|SIGCHLD|SIGTTIN|SIGTTOU|SIGIO|SIGXCPU|SIGXFSZ|SIGVTALRM|SIGPROF|SIGWINCH|SIGINFO|SIGUSR1|SIGUSR2,0x0) = 0 (0x0) 61173: sigprocmask(SIG_SETMASK,0x0,0x0) = 0 (0x0) 61173: process exit, rval = 0 ERR#4 'Interrupted system call' 57517: open("(null)",O_WRONLY,037777777777) ERR#4 'Interrupted system call' 57517: SIGNAL 14 (SIGALRM) 57517: sigreturn(0x7fffffffe080,0x10006,0x7fffffffe080,0x0,0xffff80000060386e,0x0) ERR#4 'Interrupted system call' => open() still fails in the parent, whereas the child process succeeded to open it for reading *and* closed it. The parent open() is supposed to be unblocked since the child open() succeeded, no? (... open sequence is repeated forever, it never succeed ...) -- You are receiving this mail because: You are the assignee for the bug.
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