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* [Bug nptl/14499] New: Does posix_spawn invoke atfork handlers / use vfork? @ 2012-08-20 22:24 luto at mit dot edu 2012-08-20 22:28 ` [Bug nptl/14499] " luto at mit dot edu ` (2 more replies) 0 siblings, 3 replies; 4+ messages in thread From: luto at mit dot edu @ 2012-08-20 22:24 UTC (permalink / raw) To: glibc-bugs http://sourceware.org/bugzilla/show_bug.cgi?id=14499 Bug #: 14499 Summary: Does posix_spawn invoke atfork handlers / use vfork? Product: glibc Version: unspecified Status: NEW Severity: normal Priority: P2 Component: nptl AssignedTo: unassigned@sourceware.org ReportedBy: luto@mit.edu CC: drepper.fsp@gmail.com Classification: Unclassified The resolution of bug 378 indicates that glibc's (NPTL) posix_spawn calls atfork handlers. This means that posix_spawn can't use vfork (or fancy clone options), which makes it slow. (Note that, AFAICT, this behavior is not documented anywhere, despite being implementation-specified.) This was apparently true when bug 378 was closed, but it changed in commit a9f43ef464f71b0d379524b2a6294092332c9a30. The current behavior is bizarre. See the attached code, which invokes atfork handlers only on the second posix_spawn call. IMO the right fix is to never invoke atfork handlers (since presumably nothing relies on them getting called, since they haven't been reliably called since 2005). That way vfork can be used unconditionally, which is faster. See also bug 10354, which does not have a resolution that I understand. -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug nptl/14499] Does posix_spawn invoke atfork handlers / use vfork? 2012-08-20 22:24 [Bug nptl/14499] New: Does posix_spawn invoke atfork handlers / use vfork? luto at mit dot edu @ 2012-08-20 22:28 ` luto at mit dot edu 2012-08-21 13:43 ` bugdal at aerifal dot cx 2014-06-17 5:57 ` fweimer at redhat dot com 2 siblings, 0 replies; 4+ messages in thread From: luto at mit dot edu @ 2012-08-20 22:28 UTC (permalink / raw) To: glibc-bugs http://sourceware.org/bugzilla/show_bug.cgi?id=14499 --- Comment #1 from Andy Lutomirski <luto at mit dot edu> 2012-08-20 22:28:07 UTC --- Created attachment 6593 --> http://sourceware.org/bugzilla/attachment.cgi?id=6593 Example of atfork inconsistency [There's something wrong with the bugzilla login process, so my attachment got dropped. Oops.] -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug nptl/14499] Does posix_spawn invoke atfork handlers / use vfork? 2012-08-20 22:24 [Bug nptl/14499] New: Does posix_spawn invoke atfork handlers / use vfork? luto at mit dot edu 2012-08-20 22:28 ` [Bug nptl/14499] " luto at mit dot edu @ 2012-08-21 13:43 ` bugdal at aerifal dot cx 2014-06-17 5:57 ` fweimer at redhat dot com 2 siblings, 0 replies; 4+ messages in thread From: bugdal at aerifal dot cx @ 2012-08-21 13:43 UTC (permalink / raw) To: glibc-bugs http://sourceware.org/bugzilla/show_bug.cgi?id=14499 Rich Felker <bugdal at aerifal dot cx> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |bugdal at aerifal dot cx --- Comment #2 from Rich Felker <bugdal at aerifal dot cx> 2012-08-21 13:43:08 UTC --- Indeed, while POSIX allows posix_spawn to call atfork handlers, this allowance is only for the sake of implementations that can't avoid it. Calling them is purely malevolent; it introduces opportunities for atfork-related race conditions (like the infamous malloc/fork issue) and seriously degrades performance by disallowing vfork and just from the overhead (usually heavy synchronization overhead) in the atfork handlers. Also, since posix_spawn is intended to be added to the list of async-signal-safe functions in the next version of POSIX, this allowance is surely going to vanish. It would benefit glibc to be ahead of the game and go ahead and eliminate it. -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug nptl/14499] Does posix_spawn invoke atfork handlers / use vfork? 2012-08-20 22:24 [Bug nptl/14499] New: Does posix_spawn invoke atfork handlers / use vfork? luto at mit dot edu 2012-08-20 22:28 ` [Bug nptl/14499] " luto at mit dot edu 2012-08-21 13:43 ` bugdal at aerifal dot cx @ 2014-06-17 5:57 ` fweimer at redhat dot com 2 siblings, 0 replies; 4+ messages in thread From: fweimer at redhat dot com @ 2014-06-17 5:57 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=14499 Florian Weimer <fweimer at redhat dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |fweimer at redhat dot com Flags| |security- -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2014-06-17 5:57 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2012-08-20 22:24 [Bug nptl/14499] New: Does posix_spawn invoke atfork handlers / use vfork? luto at mit dot edu 2012-08-20 22:28 ` [Bug nptl/14499] " luto at mit dot edu 2012-08-21 13:43 ` bugdal at aerifal dot cx 2014-06-17 5:57 ` fweimer at redhat dot com
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