[Bug nptl/5192] Internal lock in pthread struct is vulnerable to priority inversion

[Bug nptl/5192] Internal lock in pthread struct is vulnerable to priority inversion

[schwab@linux-m68k.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=5192

Andreas Schwab <schwab@linux-m68k.org> changed:

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         AssignedTo|drepper.fsp at gmail dot    |unassigned at sourceware
                   |com                         |dot org

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[Bug nptl/5192] Internal lock in pthread struct is vulnerable to priority inversion

[spcurry5 at linux dot vnet dot ibm dot com]

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         AssignedTo|spcurry5 at linux dot vnet  |drepper at redhat dot com
                   |dot ibm dot com             |
             Status|ASSIGNED                    |NEW


http://sourceware.org/bugzilla/show_bug.cgi?id=5192

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[Bug nptl/5192] Internal lock in pthread struct is vulnerable to priority inversion

[rsa at us dot ibm dot com]

------- Additional Comments From rsa at us dot ibm dot com  2008-04-25 20:14 -------
BZ flagged for Ulrich's attention:

http://www.sourceware.org/ml/libc-alpha/2008-04/msg00094.html

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http://sourceware.org/bugzilla/show_bug.cgi?id=5192

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[Bug nptl/5192] Internal lock in pthread struct is vulnerable to priority inversion

[spcurry5 at linux dot vnet dot ibm dot com]

------- Additional Comments From spcurry5 at linux dot vnet dot ibm dot com  2008-04-25 01:26 -------
I have a few points worth noting:

(1) I was unable to find anywhere in the POSIX specification that states the
per-thread mutex must not cause a priority inversion.
(2) Changing the pthread implementation so that every thread has a
priority-inheritance mutex, instead of a standard mutex, would cause some
performance loss due to the extra overhead associated with using
priority-inheritance mutexes. 
(3) The priority inversion situation you have described does not cause any of
the threads to hold onto a resource indefinitely, thereby preventing some other
thread from ever making forward progress. All threads eventually make forward
progress, therefore, this is more of a performance issue than a correctness
issue. So I am marking this bug as an enhancement.

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           Severity|normal                      |enhancement


http://sourceware.org/bugzilla/show_bug.cgi?id=5192

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[Bug nptl/5192] Internal lock in pthread struct is vulnerable to priority inversion

[spcurry5 at linux dot vnet dot ibm dot com]

------- Additional Comments From spcurry5 at linux dot vnet dot ibm dot com  2008-04-25 00:27 -------
Example test case (priority-inversion.c) confirmed. A priority inversion occurs,
causing the high-priority third thread to wait on the low-priority first thread.

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[Bug nptl/5192] Internal lock in pthread struct is vulnerable to priority inversion

[spcurry5 at linux dot vnet dot ibm dot com]

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         AssignedTo|drepper at redhat dot com   |spcurry5 at linux dot vnet
                   |                            |dot ibm dot com
             Status|NEW                         |ASSIGNED


http://sourceware.org/bugzilla/show_bug.cgi?id=5192

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[Bug nptl/5192] Internal lock in pthread struct is vulnerable to priority inversion

[ismail at pardus dot org dot tr]

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                 CC|                            |ismail at pardus dot org dot
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http://sourceware.org/bugzilla/show_bug.cgi?id=5192

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[Bug nptl/5192] Internal lock in pthread struct is vulnerable to priority inversion

[matt dot hoosier at gmail dot com]

------- Additional Comments From matt dot hoosier at gmail dot com  2007-10-17 15:52 -------
Created an attachment (id=2048)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=2048&action=view)
Example to illustrate priority inversion in NPTL pthread internals


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