Bug #55614 [Fbk->NoF]: pcntl_signal() + fgetc() is not allowing me to break with CTRL+C

Edit report at https://bugs.php.net/bug.php?id=55614&edit=1 ID: 55614 Updated by: php-bugs@lists.php.net Reported by: i3367890 at gmail dot com Summary: pcntl_signal() + fgetc() is not allowing me to break with CTRL+C -Status: Feedback +Status: No Feedback Type: Bug Package: PCNTL related Operating System: (Arch, Debian) Linux PHP Version: 5.3.8 - 8.0.7 Assigned To: cmb Private report: N New Comment: No feedback was provided. The bug is being suspended because we assume that you are no longer experiencing the problem. If this is not the case and you are able to provide the information that was requested earlier, please do so and change the status of the bug back to "Re-Opened". Thank you. Previous Comments: ------------------------------------------------------------------------ [2021-07-08 10:17:27] cmb@php.net Yeah, sorry, very long time to respond. Anyhow, this can't work, because you're using ticks as signal handler, and there is no tick executed while fgets() waits for input. Did you try with pcntl_async_signals(true) That may work, but according to a comment on bug #49340, it does not. ------------------------------------------------------------------------ [2021-07-08 06:21:26] i3367890 at gmail dot com Wow, I completely forgot about posting this. Thanks for following up. Unfortunately it does still seem to be hanging around. $ php --version PHP 8.0.7 (cli) (built: Jun 4 2021 23:17:30) ( NTS ) Copyright (c) The PHP Group Zend Engine v4.0.7, Copyright (c) Zend Technologies with Zend OPcache v8.0.7, Copyright (c), by Zend Technologies (This is from deb.sury.org. I'm on Debian now.) $ php -r "declare(ticks = 1); function quit() { print \"X\\n\"; die; } pcntl_signal(SIGINT, \"quit\"); fgetc(STDIN);" ^C^C^C^C^C^C^\Quit $ _ Continuous ^C^C^C still simply retries forever: PHP tty | strace tty | ... | rt_sigprocmask(SIG_UNBLOCK, [INT], NULL, 8) = 0 | read(0, 0x7fd24947f000, 8192) = ? ERESTARTSYS (To be restarted if SA_RESTART is set) ^C ---------------^ | --- SIGINT {si_signo=SIGINT, si_code=SI_KERNEL} --- | rt_sigreturn({mask=[]}) = 0 | read(0, 0x7fd24947f000, 8192) = ? ERESTARTSYS (To be restarted if SA_RESTART is set) ^C ---------------^ | --- SIGINT {si_signo=SIGINT, si_code=SI_KERNEL} --- | rt_sigreturn({mask=[]}) = 0 | read(0, 0x7fd24947f000, 8192) = ? ERESTARTSYS (To be restarted if SA_RESTART is set) ^C ---------------^ | --- SIGINT {si_signo=SIGINT, si_code=SI_KERNEL} --- | rt_sigreturn({mask=[]}) = 0 | read(0, "x\n", 8192) = 2 'x' + ------------^ <Return> | rt_sigprocmask(SIG_BLOCK, ~[RTMIN RT_1], [], 8) = 0 Exit-> | write(1, "X\n", 2) = 2 | rt_sigprocmask(SIG_BLOCK, ~[RTMIN RT_1], ~[KILL STOP RTMIN RT_1], 8) = 0 | rt_sigprocmask(SIG_SETMASK, ~[KILL STOP RTMIN RT_1], NULL, 8) = 0 | rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 | close(2) = 0 | close(1) = 0 | close(0) = 0 | munmap(..., ...) = 0 | ... (NB, the note about stty cbreak at the end of the 2nd comment is somewhat orthogonal to this bug; inputting any text then pressing Return IMO suffices to demonstrate that normal input is consumed correctly.) Setting restart_signals to false still consumes one ^C before responding correctly to the second: $ strace -o /dev/pts/26 php -r "declare(ticks = 1); function quit() { print \"X\\n\"; die; } pcntl_signal(SIGINT, \"quit\", 0); fgetc(STDIN);" ^C^CX PHP tty | strace tty | rt_sigprocmask(SIG_UNBLOCK, [INT], NULL, 8) = 0 | read(0, 0x7f66fb47e000, 8192) = ? ERESTARTSYS (To be restarted if SA_RESTART is set) ^C 1 -------------^ | --- SIGINT {si_signo=SIGINT, si_code=SI_KERNEL} --- | rt_sigreturn({mask=[]}) = -1 EINTR (Interrupted system call) | read(0, 0x7f66fb47e000, 8192) = ? ERESTARTSYS (To be restarted if SA_RESTART is set) ^C 2 -------------^ | --- SIGINT {si_signo=SIGINT, si_code=SI_KERNEL} --- | rt_sigreturn({mask=[]}) = -1 EINTR (Interrupted system call) | rt_sigprocmask(SIG_BLOCK, ~[RTMIN RT_1], [], 8) = 0 Exit-> | write(1, "X\n", 2) = 2 | rt_sigprocmask(SIG_BLOCK, ~[RTMIN RT_1], ~[KILL STOP RTMIN RT_1], 8) = 0 | rt_sigprocmask(SIG_SETMASK, ~[KILL STOP RTMIN RT_1], NULL, 8) = 0 | rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 | close(2) = 0 | close(1) = 0 | close(0) = 0 | munmap(0x7f66f7cb7000, 29808) = 0 | munmap(0x7f66f7cbf000, 16592) = 0 ------------------------------------------------------------------------ [2021-07-06 16:18:40] cmb@php.net Is this still an issue with any of the actively supported PHP versions[1]? [1] <https://www.php.net/supported-versions.php> ------------------------------------------------------------------------ [2011-09-06 03:24:59] i3367890 at gmail dot com I forgot to mention something! In the first script pressing a key (any key) causes PHP to shut down properly. Here's what it looks like: My console | strace console | (....) | rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 | read(0, 0x8b825f8, 8192) = ? ERESTARTSYS (To be restarted) ^C ---------------^ | --- SIGINT (Interrupt) @ 0 (0) --- I | sigreturn() = ? (mask now []) pressed | read(0, "d", 8192) = 1 "d" -------------^ | rt_sigprocmask(SIG_BLOCK, ~[RTMIN RT_1], [], 8) = 0 ! --> | write(1, "X\n", 2) = 2 | rt_sigprocmask(SIG_BLOCK, ~[RTMIN RT_1], ~[KILL STOP RTMIN RT_1], 8) = 0 | rt_sigprocmask(SIG_SETMASK, ~[KILL STOP RTMIN RT_1], NULL, 8) = 0 | close(2) = 0 My console | strace console | (....) ======= NOTE: ======= If fgetc(STDIN) does not return immediately after a single character - it doesn't on my system, it waits for a newline - you might need to run "stty cbreak". When you're done run "stty -cbreak" if you want to switch whatever cbreak does back off, or just close the terminal. i336 ------------------------------------------------------------------------ [2011-09-06 03:15:08] i3367890 at gmail dot com Description: ------------ Running the following code at the commandline as demonstrated simply does not work for me. It gobbles up all presses of ^C and will not quit (^\ ie CTRL+\ produces SIGQUIT and is useful in this situation): php -r "declare(ticks = 1); function quit() { print \"X\\n\"; die; } pcntl_signal(SIGINT, \"quit\"); fgetc(STDIN);" Running the following, on the other hand, works for me just fine. php -r "declare(ticks = 1); function quit() { print \"X\\n\"; die; } pcntl_signal(SIGINT, \"quit\"); while(1) { sleep(1); };" Pressing ^C shuts the script down nicely. I see no problems with the first code example. It should work, right? Here's what strace is saying: My console | strace console | (....) | rt_sigprocmask(SIG_BLOCK, ~[RTMIN RT_1], [], 8) = 0 | rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 | read(0, 0x943e5f4, 8192) = ? ERESTARTSYS (To be restarted) | --- SIGINT (Interrupt) @ 0 (0) --- | sigreturn() = ? (mask now []) | read(0, 0x943e5f4, 8192) = ? ERESTARTSYS (To be restarted) ^C ---------------^ | --- SIGINT (Interrupt) @ 0 (0) --- | sigreturn() = ? (mask now []) | read(0, 0x943e5f4, 8192) = ? ERESTARTSYS (To be restarted) ^C ---------------^ | --- SIGINT (Interrupt) @ 0 (0) --- | sigreturn() = ? (mask now []) | read(0, (waiting) ---------^ It gets even more interesting. Setting parameter 3 to pcntl_signal, restart_signals, to false makes PHP gobble up one ^C *then* quit: php -r "declare(ticks = 1); function quit() { print \"X\\n\"; die; } pcntl_signal(SIGINT, \"quit\", 0); fgetc(STDIN);" Like so: My console | strace console | (...) | rt_sigprocmask(SIG_BLOCK, ~[RTMIN RT_1], [], 8) = 0 | rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 | rt_sigaction(SIGINT, {0x82d8690, ~[RTMIN RT_1], SA_INTERRUPT}, {SIG_DFL, [], 0}, 8) = 0 | rt_sigprocmask(SIG_BLOCK, ~[RTMIN RT_1], [], 8) = 0 | rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 | read(0, 0x9e985f8, 8192) = ? ERESTARTSYS (To be restarted) ^C --------------^ | --- SIGINT (Interrupt) @ 0 (0) --- | sigreturn() = ? (mask now []) | read(0, 0x9e985f8, 8192) = ? ERESTARTSYS (To be restarted) ^C --------------^ | --- SIGINT (Interrupt) @ 0 (0) --- | sigreturn() = ? (mask now []) | rt_sigprocmask(SIG_BLOCK, ~[RTMIN RT_1], [], 8) = 0 ! --> | write(1, "X\n", 2) = 2 | rt_sigprocmask(SIG_BLOCK, ~[RTMIN RT_1], ~[KILL STOP RTMIN RT_1], 8) = 0 | rt_sigprocmask(SIG_SETMASK, ~[KILL STOP RTMIN RT_1], NULL, 8) = 0 | close(2) = 0 | close(1) = 0 | (...) As you can see from my exclamation, *the custom quit function is WORKING* in the second example, just not straight away. PHP seems to be having indigestion with the restart_syscalls bit...? I wasn't sure what to put in what boxes since there were multiple scripts and backtraces (if you could call them such) so I put them all here. Hope that's okay. i336 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=55614&edit=1