[Bug 675185] Re: [Hardy SRU] dash bug causes mysqld_safe to spin at 100% CPU

[Shahriyar Rzayev]

Percona now uses JIRA for bug reports so this bug report is migrated to:
https://jira.percona.com/browse/PS-1164

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Title:
  [Hardy SRU] dash bug causes mysqld_safe to spin at 100% CPU

Status in MariaDB:
  Fix Released
Status in Percona Server moved to https://jira.percona.com/projects/PS:
  Invalid
Status in Percona Server moved to https://jira.percona.com/projects/PS 5.1 series:
  Invalid
Status in Percona Server moved to https://jira.percona.com/projects/PS 5.5 series:
  Invalid
Status in dash package in Ubuntu:
  Invalid
Status in mysql-5.1 package in Ubuntu:
  Invalid

Bug description:
  Symptoms are: After mysql server upgrades + restarts the old mysqld_safe keeps running and consumes 100% cpu, strace shows:
  wait4(4294967295, 0x7fffb3b3d59c, 0, NULL) = -1 ECHILD (No child ...
  wait4(4294967295, 0x7fffb3b3d59c, 0, NULL) = -1 ECHILD (No child ...
  wait4(4294967295, 0x7fffb3b3d59c, 0, NULL) = -1 ECHILD (No child ...
  For more info see the dupes, particularily bug 105457. Does not happen always, for reliable test case see below.

  This is a bug (race condition) in dash, partly fixed by
  http://git.kernel.org/?p=utils/dash/dash.git;a=commit;h=3800d4934391b144fd261a7957aea72ced7d47ea
  . This fixes the test case and mysqld_safe, but introduces another
  regression: http://eeek.borgchat.net/lists/dash/msg00268.html (patch
  for that in the thread)

  TEST CASE: Script in the commit message (link above). Allows to
  reproduce this always, even on Karmic still.

  (Proposed fix of using #!/bin/bash instead of #!/bin/sh is not as
  straigtforward as expected. bash called as sh goes into sh
  compatibility mode, called as bash it may behave subtle differently)

  NOTES: mysqld_safe was replaced by an upstart job in Lucid. But Hardy
  has support for 3 more years, justifiying a fix.

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