Re: BUG: bash-4.0.17 and SIGWINCH during initialization

[Chet Ramey]

Nicolai Lissner 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-unknown-linux-gnu' 
> -DCONF_VENDOR='unknown' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' 
> -DSHELL -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib   -march=athlon64 -O2 
> -pipe -fPIC
> uname output: Linux lilith 2.6.29.1 #1 PREEMPT Fri Apr 3 03:32:29 CEST 2009 
> x86_64 AMD Athlon(tm) Processor LE-1620 AuthenticAMD GNU/Linux
> Machine Type: x86_64-unknown-linux-gnu
> 
> Bash Version: 4.0
> Patch Level: 17
> Release Status: release
> 
> Description: 
> 
> There is some kind of race condition in bash-4 
> (or maybe even readline) when it receives SIGWINCH 
> during initialization. 

Not a race condition exactly, but a timing issue.  The problem occurs
when a SIGWINCH arrives during redisplay.  The SIGWINCH handler tries
to update the display immediately to reflect the new window size, but
steps on itself when calling the redisplay code recursively.  A simple
semaphore is enough to prevent the double calls.

Try the attached patch and let me know how it works.

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/lib/readline/readline.h 2009-01-04 14:32:33.000000000 
-0500
--- lib/readline/readline.h     2009-04-13 08:47:00.000000000 -0400
***************
*** 815,820 ****
  #define RL_STATE_MULTIKEY     0x200000        /* reading multiple-key command 
*/
  #define RL_STATE_VICMDONCE    0x400000        /* entered vi command mode at 
least once */
  
! #define RL_STATE_DONE         0x800000        /* done; accepted line */
  
  #define RL_SETSTATE(x)                (rl_readline_state |= (x))
--- 815,821 ----
  #define RL_STATE_MULTIKEY     0x200000        /* reading multiple-key command 
*/
  #define RL_STATE_VICMDONCE    0x400000        /* entered vi command mode at 
least once */
+ #define RL_STATE_REDISPLAYING 0x800000        /* updating terminal display */
  
! #define RL_STATE_DONE         0x1000000       /* done; accepted line */
  
  #define RL_SETSTATE(x)                (rl_readline_state |= (x))
*** ../bash-4.0-patched/lib/readline/display.c  2009-01-04 14:32:32.000000000 
-0500
--- lib/readline/display.c      2009-04-13 08:29:54.000000000 -0400
***************
*** 513,516 ****
--- 513,517 ----
       data structures. */
    _rl_block_sigint ();  
+   RL_SETSTATE (RL_STATE_REDISPLAYING);
  
    if (!rl_display_prompt)
***************
*** 1237,1240 ****
--- 1238,1242 ----
    }
  
+   RL_UNSETSTATE (RL_STATE_REDISPLAYING);
    _rl_release_sigint ();
  }
*** ../bash-4.0-patched/lib/readline/terminal.c 2009-01-04 14:32:34.000000000 
-0500
--- lib/readline/terminal.c     2009-04-13 08:43:00.000000000 -0400
***************
*** 356,360 ****
        if (CUSTOM_REDISPLAY_FUNC ())
        rl_forced_update_display ();
!       else
        _rl_redisplay_after_sigwinch ();
      }
--- 356,360 ----
        if (CUSTOM_REDISPLAY_FUNC ())
        rl_forced_update_display ();
!       else if (RL_ISSTATE(RL_STATE_REDISPLAYING) == 0)
        _rl_redisplay_after_sigwinch ();
      }