Bug 460744 - nash misunderstands ppoll() semantics and goes bonkers as a result
nash misunderstands ppoll() semantics and goes bonkers as a result
Product: Fedora
Classification: Fedora
Component: mkinitrd (Show other bugs)
All Linux
medium Severity medium
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Assigned To: Peter Jones
Fedora Extras Quality Assurance
Depends On:
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Reported: 2008-08-30 15:30 EDT by Arjan van de Ven
Modified: 2009-07-14 10:33 EDT (History)
2 users (show)

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Doc Type: Bug Fix
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Last Closed: 2009-07-14 10:33:14 EDT
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Description Arjan van de Ven 2008-08-30 15:30:21 EDT
Description of problem:

the ppoll() syscall (similar to select and pselect) modifies the content of the timeout argument and it puts in that the time left from the timeout when an event came in.

glibc hides this behavior from applications by making the system call work  
on a copy, but nash uses the system call directly.
the problem is that nash tends to use ppoll in loops and the timeout doesn't 
get reset each time by nash, so if an event comes in just before the exipiry 
of the timer... it then will always ask for near zero time in the future.


        pd.revents = 0;
        while ((rc = nash_ppoll(&pd, 1, top, NULL, 0) < 0)) {
            if (errno != EINTR)
                return -1;        
Comment 1 Arjan van de Ven 2008-08-30 17:58:34 EDT
ok it's even worse than I thought ;(

some places in nash *depend* on the timeout being overwritten, while other places in nash depend on it *not* being overwritten for certain error cases.
Interesting ;(
Comment 2 Bug Zapper 2009-06-09 22:35:10 EDT
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Comment 3 Bug Zapper 2009-07-14 10:33:14 EDT
Fedora 9 changed to end-of-life (EOL) status on 2009-07-10. Fedora 9 is 
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