Re: DEBUG trap breaks pipelines

[Chet Ramey]

lex@upc.ua wrote:
> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: linux-gnu
> Compiler: gcc
> Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' 
> -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-redhat-linux-gnu' 
> -DCONF_VENDOR='redhat' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' 
> -DSHELL -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib  -D_GNU_SOURCE  -O2 -g 
> -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector 
> --param=ssp-buffer-size=4 -m64 -mtune=generic
> uname output: Linux fiber.upc.intranet 2.6.20-1.2320.fc5 #1 SMP Tue Jun 12 
> 18:50:49 EDT 2007 x86_64 x86_64 x86_64 GNU/Linux
> Machine Type: x86_64-redhat-linux-gnu
> 
> Bash Version: 3.1
> Patch Level: 17
> Release Status: release
> 
> Note: Configuration Information is irrelevant -- same bug in all 
> versions(3.1-4.0 inclusive)/OSes(linux,tru64)/machines(alpha,i686,x86_64).
> 
> Description:
>       {trap "/external/program" DEBUG} breaks pipelining in some ways. When 
> trap is set:
> 
>         1. A | B pipeline sometimes(*) does not run(**) second part and hungs 
> forever.
>            sometimes SIGINT(Ctrl+C) revives it, and second part starts.
>            (*) in my observation it depends on time, 'A' takes to complete -- 
> "small" tasks does not triggers that behaviour.
>            (**) trap for the "B" part is called, but not the command "B" 
> itself
>         2. A & B breaks job control
>       3. (may be not a bug) "$_" no longer contains last arg.

This was interesting.  See if the attached patch fixes 1 and 2.

Chet

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer

Chet Ramey, ITS, CWRU    chet@case.edu    http://cnswww.cns.cwru.edu/~chet/

*** ../bash-4.0-patched/jobs.c  2009-01-29 17:09:49.000000000 -0500
--- jobs.c      2009-04-11 15:14:27.000000000 -0400
***************
*** 443,447 ****
    the_pipeline = saved_pipeline;
    already_making_children = saved_already_making_children;
!   if (discard)
      discard_pipeline (old_pipeline);
  }
--- 443,447 ----
    the_pipeline = saved_pipeline;
    already_making_children = saved_already_making_children;
!   if (discard && old_pipeline)
      discard_pipeline (old_pipeline);
  }
*** ../bash-4.0-patched/trap.c  2009-01-16 17:07:53.000000000 -0500
--- trap.c      2009-04-11 15:11:58.000000000 -0400
***************
*** 799,802 ****
--- 799,803 ----
  {
    int trap_exit_value;
+   pid_t save_pgrp;
  
    /* XXX - question:  should the DEBUG trap inherit the RETURN trap? */
***************
*** 804,808 ****
--- 805,820 ----
    if ((sigmodes[DEBUG_TRAP] & SIG_TRAPPED) && ((sigmodes[DEBUG_TRAP] & 
SIG_IGNORED) == 0) && ((sigmodes[DEBUG_TRAP] & SIG_INPROGRESS) == 0))
      {
+ #if defined (JOB_CONTROL)
+       save_pgrp = pipeline_pgrp;
+       pipeline_pgrp = shell_pgrp;
+       save_pipeline (1);
+       stop_making_children ();
+ #endif
        trap_exit_value = _run_trap_internal (DEBUG_TRAP, "debug trap");
+ #if defined (JOB_CONTROL)
+       pipeline_pgrp = save_pgrp;
+       restore_pipeline (1);
+       notify_and_cleanup ();
+ #endif
        
  #if defined (DEBUGGER)