Date: Thu, 7 Oct 2004 19:49:39 GMT From: Mark Gooderum <mark@verniernetworks.com> To: freebsd-gnats-submit@FreeBSD.org Subject: threads/72429: threads blocked in stdio (fgets, etc) are not cancellable in 5.3 (works in 4.x) Message-ID: <200410071949.i97Jndpw004041@www.freebsd.org> Resent-Message-ID: <200410071950.i97JoR03079645@freefall.freebsd.org>
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>Number: 72429 >Category: threads >Synopsis: threads blocked in stdio (fgets, etc) are not cancellable in 5.3 (works in 4.x) >Confidential: no >Severity: serious >Priority: low >Responsible: freebsd-threads >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Thu Oct 07 19:50:27 GMT 2004 >Closed-Date: >Last-Modified: >Originator: Mark Gooderum >Release: 5.3 Beta 6 >Organization: Vernier Networks, Inc. >Environment: FreeBSD 172.20.1.199 5.3-BETA6 FreeBSD 5.3-BETA6 #0: Thu Oct 7 09:35:49 PDT 2004 root@eagle.jumpadmin.net:/usr/build/ambit2/freebsd5/sys/i386/compile/VNISMP i386 >Description: With libc_r in 4.9 a function blocked in stdio (say fgets()) is cancellable. The call from fgets() to the I/O in FreeBSD 4.9 with libc/libc_r: fgets() __srefill() __sread() (via fp->_read()) _read() (now in libc_r) calls thread_enter_cancellation_point() calls __read() __read() does the uthread I/O voodoo thread can be cancelled... With FreeBSD 5.3 libc/libpthread: fgets() __srefill() __sread() (via fp->_read()) _read() - weak symbol for __sys_read() in libc (libpthread only defines __read and a weak reference from read to __read) thread can't be cancelled - it's blocked in real system call and thread_enter_cancellation_point() was never called With FreeBSD 5.3 libc/libpthread: fgets() __srefill() __sread() (via fp->_read()) _read() (now in libc_r) _read() does the uthread I/O voodoo thread can't be cancelled as thread_enter_cancellation_point() was never called, that is in __read()... >How-To-Repeat: Try to pthread_cancel() a thread blocked in any stdio operation (fgets, fread, etc), it will never cancel. >Fix: Given the current conventions for _foo, __foo and foo it seems like __sread et. al. should be calling the foo() versions of the functions so they get wrapped as cancellation points. >Release-Note: >Audit-Trail: >Unformatted:
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