Details
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Type:
Bug
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Status: Closed
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Priority:
Minor
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Resolution: Fixed
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Affects Version/s: None
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Fix Version/s: None
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Component/s: None
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Labels:
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 #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.
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Re: [Hardy SRU] dash bug causes mysqld_safe to spin at 100% CPU
I fixed this for mariadb by adding a patch to the .deb packaging that puts #!/bin/bash in the header of mysqld_safe.
Fix will be available from 5.1.52 and 5.2.4.
Re: [Hardy SRU] dash bug causes mysqld_safe to spin at 100% CPU
Fixed in MariaDB 5.2.4 and 5.1.53
Re: [Hardy SRU] dash bug causes mysqld_safe to spin at 100% CPU
I tested the testcase in the commit on Precise and there seem to no issue there
(probably fixed there).
Also, it is not the right approach to change #Unable to render embedded object: File (/bin/sh to #) not found./bin/bash since
former invokes POSIX compatibility mode and if dash has problems on any
platform, then that should be fixed rather than changing it in mysqld_safe or
#!/bin/sh needs to pointed elsewhere (or with update-alternatives).
Regarding the init scripts, I see that Percona Server is not packaged with
upstart script (hence vulnerable to this if on a platform with a buggy dash) as
mysql-server-55 does. I will open a separate issue to add that.
Re: [Hardy SRU] dash bug causes mysqld_safe to spin at 100% CPU
lp:1053183 is the issue for providing upstart scripts with percona-server.
Launchpad bug id: 675185
fix.diff
LPexportBug675185_fix.diff