[uClibc 0000716]: libc/misc/utmp/utent.c deadlocks when used with libpthread

[bugs at busybox.net]

The following issue has been SUBMITTED. 
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http://busybox.net/bugs/view.php?id=716 
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Reported By:                rholzmann
Assigned To:                uClibc
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Project:                    uClibc
Issue ID:                   716
Category:                   Other
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     assigned
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Date Submitted:             02-10-2006 10:49 PST
Last Modified:              02-10-2006 10:49 PST
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Summary:                    libc/misc/utmp/utent.c deadlocks when used with
libpthread
Description: 
utent.c has a few problems with mutex locking when used in a binary that
was linked with pthreads.  The are a few deadlock conditions where
functions may be called which lock the utmplock but never release it and
where a function that hold the lock calls other functions which try to
relock the same lock.  Here is one example in the function __getutent:

static struct utmp *__getutent(int utmp_fd)
{
    if (utmp_fd == -1) {
        setutent();
    }
    if (utmp_fd == -1) {
        return NULL;
    }

    LOCK;
    if (read(utmp_fd, (char *) &static_utmp, sizeof(struct utmp)) != 
                sizeof(struct utmp))
    {
        return NULL;
    }

    UNLOCK;
    return &static_utmp;
}

Notice the error condition does not unlock the semaphore.  The problem is
not visible when pthreads isn't used since the lock/unlock functions are
NOOP functions.

I have attached a patch file that tries to correct these problems.  I
think the patch fixes all of the possible deadlock conditions.  Let me
know what you think.

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Issue History 
Date Modified   Username       Field                    Change               
====================================================================== 
02-10-06 10:49  rholzmann      New Issue                                    
02-10-06 10:49  rholzmann      Status                   new => assigned     
02-10-06 10:49  rholzmann      Assigned To               => uClibc          
02-10-06 10:49  rholzmann      File Added: utmp-thread.patch                    
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