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

Jakob Unterwurzacher jakobunt at gmail.com
Mon Nov 22 10:58:04 GMT 2010


Thing is, mysqld_safe isn't used anymore since Lucid as upstart has
taken over (the file is still there though).

** Description changed:

  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, fixed by
+ 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.
  
  SRU JUSTIFICATION: Obviously safe patch.
  
  PATCH: Attached, run mysqld_safe in bash instead of dash.
  
  REGRESSION POTENTIAL: Minimal. 1) Bash is a superset of dash. 2) Before
  dash became the default sh, bash was used, we just revert that change.
  
  NOTES: mysqld_safe will be replaced by an upstart job. But Hardy has
  support for 3 more years, justifiying a fix.

** Description changed:

  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.
  
  SRU JUSTIFICATION: Obviously safe patch.
  
  PATCH: Attached, run mysqld_safe in bash instead of dash.
  
  REGRESSION POTENTIAL: Minimal. 1) Bash is a superset of dash. 2) Before
  dash became the default sh, bash was used, we just revert that change.
  
- NOTES: mysqld_safe will be replaced by an upstart job. But Hardy has
- support for 3 more years, justifiying a fix.
+ NOTES: mysqld_safe was replaced by an upstart job in Lucid. But Hardy
+ has support for 3 more years, justifiying a fix.

-- 
[Hardy SRU] dash bug causes mysqld_safe to spin at 100% CPU
https://bugs.launchpad.net/bugs/675185
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