Debian Bug report logs - #283702
Race condition when writing ~/.bash_history

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Message #5 received at submit@bugs.debian.org (full text, mbox, reply):

From: Cyril Bouthors <cyb@debian.org>

To: Debian Bug Tracking System <submit@bugs.debian.org>

Subject: Race condition when writing ~/.bash_history

Date: Tue, 30 Nov 2004 21:25:46 +0300

Package: bash
Version: 3.0-10
Severity: critical
Justification: causes serious data loss

Hi,

About once a month, my ~/.bash_history gets empty.  This is quite
annoying because I'm using C-r really often.

I get the same problem again and again for quite some time now, maybe
two years.

I think it comes from the fact that I'm not using a typical setup.
I'm running 5 different "bash --noediting -i" under Emacs with
shell-mode buffers and I'm often exiting Emacs without closing all the
shells by hand.  The 5 bash processes get killed and I guess they try
to write ~/.bash_history at the exact same time.

I think it's a basic race condition, bash should lock the file before
trying to write it but I haven't checked if it does.

I haven't reproduced the exact same bug where ~/.bash_history gets
empty but a similar unwanted behaviour can be reproduced by doing
massive parallel "history -w" with:

cyb@wide:~$ export HISTFILE=/tmp/history
cyb@wide:~$ export HISTSIZE=100000
cyb@wide:~$ rm -f $HISTFILE
cyb@wide:~$ for a in `seq 5`; do xterm -e 'for a in `seq 1000`; do echo "echo $a; history -w"; done | bash -i' ; done
cyb@wide:~$ wc -l $HISTFILE
10000 /tmp/history
cyb@wide:~$ rm $HISTFILE
cyb@wide:~$ for a in `seq 5`; do xterm -e 'for a in `seq 1000`; do echo "echo $a; history -w"; done | bash -i' & done
[1] 4715
[2] 4721
[3] 4722
[4] 4723
[5] 4724
cyb@wide:~$ wait
[1]   Done                    xterm -e 'for a in `seq 1000`; do echo "echo $a; history -w"; done | bash -i'
[2]   Done                    xterm -e 'for a in `seq 1000`; do echo "echo $a; history -w"; done | bash -i'
[4]-  Done                    xterm -e 'for a in `seq 1000`; do echo "echo $a; history -w"; done | bash -i'
[5]+  Done                    xterm -e 'for a in `seq 1000`; do echo "echo $a; history -w"; done | bash -i'
[3]+  Done                    xterm -e 'for a in `seq 1000`; do echo "echo $a; history -w"; done | bash -i'
cyb@wide:~$ wc -l $HISTFILE
2794 /tmp/history
cyb@wide:~$ unset HISTFILE
cyb@wide:~$

/tmp/history should be 10k lines long in both cases (5*1000*2).

Regards

-- System Information:
Debian Release: 3.1
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: i386 (i686)
Kernel: Linux 2.6.9-1-686
Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968)

Versions of packages bash depends on:
ii  base-files                  3.1.0        Debian base system miscellaneous f
ii  libc6                       2.3.2.ds1-18 GNU C Library: Shared libraries an
ii  libncurses5                 5.4-4        Shared libraries for terminal hand
ii  passwd                      1:4.0.3-30.4 Change and administer password and

-- no debconf information

Message #10 received at 283702@bugs.debian.org (full text, mbox, reply):

From: Peter Walser <peterwalser@yahoo.com>

To: 283702@bugs.debian.org

Subject: bash-history not thread save?

Date: Wed, 1 Dec 2004 16:52:11 +0100

As far as I understand uses bash/history the function readline.

with bash 2.05b.0 :
[... steps described above ...]
$ wc -l $HISTFILE
2805 /tmp/history

So I get quite the same behavior.

I think readline/history is not thread save, but it's not critical.


Regards

Peter

Message #17 received at 283702@bugs.debian.org (full text, mbox, reply):

From: Cyril Bouthors <cyril@bouthors.org>

To: 283702@bugs.debian.org

Subject: Forward to upstream?

Date: Thu, 09 Dec 2004 19:17:38 +0300

[Message part 1 (text/plain, inline)]

This is a bug in upstream, maybe we should forward this to upstream
authors, they'll probably have a good reactivity.
-- 
Cyril Bouthors

[Message part 2 (application/pgp-signature, inline)]

Message #22 received at 283702@bugs.debian.org (full text, mbox, reply):

From: Chet Ramey <chet.ramey@case.edu>

To: Cyril Bouthors <cyb@debian.org>, 283702@bugs.debian.org

Subject: Re: Bug#283702: Race condition when writing ~/.bash_history (forwarded from Cyril Bouthors)

Date: Fri, 09 Sep 2005 20:55:40 -0400

Matthias Klose wrote:
> [severity was lowerd in the Debian BTS]

I'm not inclined to do anything about this.

Chet
-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
( ``Discere est Dolere'' -- chet )
						Live Strong.
Chet Ramey, ITS, CWRU    chet@case.edu    http://cnswww.cns.cwru.edu/~chet/

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