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

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 #Unable to render embedded object: File (/bin/bash instead of #) not found./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.