On 07/29/2012 12:46 AM, Chet Ramey wrote: > On 7/27/12 9:50 AM, Michael Haubenwallner wrote: > >> With attached patch I haven't been able to break the testcase below so far >> on that AIX 6.1 box here. >> >> But still, the other one using the $()-childs still fails. > > Try the attached patch for that.
Collecting the patches and cleaning up now unused code, attached patch seems to fix both CHILD_MAX related problems on that AIX box here now, without using the RECYCLES_PIDS workaround. Thank you! /haubi/
Bash assumes pids aren't reused before sysconf(_SC_CHILD_MAX) immediate childs (the dynamic value), as well as ascending and wrapped around pid values. However, as specified by POSIX, conforming kernels actually guarantee for CHILD_MAX imediate childs (the static value) before reusing pids. Additionally, AIX (at least) does not guarantee for ascending pid values at all. Actually, AIX reuses pids after its CHILD_MAX value of 128 in somewhat random order in some configuration- or load-cases, resulting in race conditions like these: http://lists.gnu.org/archive/html/bug-bash/2008-07/msg00117.html This looks like a similar problem with Cygwin, where RECYCLES_PIDS is defined as the workaround, but that isn't really correct for AIX (and maybe Interix): http://www.cygwin.com/ml/cygwin/2004-09/msg00882.html http://www.cygwin.com/ml/cygwin/2002-08/msg00449.html *** jobs.c.orig 2012-08-20 16:23:51 +0200 --- jobs.c 2012-08-20 16:51:36 +0200 *************** *** 317,324 **** static char retcode_name_buffer[64]; - /* flags to detect pid wraparound */ - static pid_t first_pid = NO_PID; - static int pid_wrap = -1; - #if !defined (_POSIX_VERSION) --- 317,320 ---- *************** *** 347,352 **** { js = zerojs; - first_pid = NO_PID; - pid_wrap = -1; } --- 343,346 ---- *************** *** 1823,1833 **** as the proper pgrp if this is the first child. */ - if (first_pid == NO_PID) - first_pid = pid; - else if (pid_wrap == -1 && pid < first_pid) - pid_wrap = 0; - else if (pid_wrap == 0 && pid >= first_pid) - pid_wrap = 1; - if (job_control) { --- 1817,1820 ---- *************** *** 1863,1875 **** #endif ! if (pid_wrap > 0) ! delete_old_job (pid); ! #if !defined (RECYCLES_PIDS) ! /* Only check for saved status if we've saved more than CHILD_MAX ! statuses, unless the system recycles pids. */ ! if ((js.c_reaped + bgpids.npid) >= js.c_childmax) ! #endif ! bgp_delete (pid); /* new process, discard any saved status */ last_made_pid = pid; --- 1850,1856 ---- #endif ! delete_old_job (pid); ! bgp_delete (pid); /* new process, discard any saved status */ last_made_pid = pid; *** execute_cmd.c.orig 2012-08-20 16:36:10 +0200 --- execute_cmd.c 2012-08-20 16:51:14 +0200 *************** *** 742,748 **** /* XXX - this is something to watch out for if there are problems ! when the shell is compiled without job control. */ ! if (already_making_children && pipe_out == NO_PIPE && ! last_made_pid != last_pid) { stop_pipeline (asynchronous, (COMMAND *)NULL); --- 742,750 ---- /* XXX - this is something to watch out for if there are problems ! when the shell is compiled without job control. Don't worry about ! whether or not last_made_pid == last_pid; already_making_children ! tells us whether or not there are unwaited-for children to wait ! for and reap. */ ! if (already_making_children && pipe_out == NO_PIPE) { stop_pipeline (asynchronous, (COMMAND *)NULL);
