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Date:	Mon, 1 Dec 2008 21:41:53 +0100
From:	"kalle ko" <cocalle AT gmail DOT com>
To:	cygwin AT cygwin DOT com
Subject:	pthread_rwlock_rdlock() returns EDEADLK when trying to call it > once
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Possible bug in winsup/cygwin/thread.cc:
...
int
pthread_rwlock::rdlock ()
{
  int result = 0;
  struct RWLOCK_READER *reader;
  pthread_t self = pthread::self ();

  mtx.lock ();

  if (lookup_reader (self))
    {
      result = EDEADLK;
      goto DONE;
    }
...

It doesn't seem like it's possible for a thread to call
pthread_rwlock_rdlock() multiple times, and if a thread does, it will get
a EDEADLK error.

http://opengroup.org/onlinepubs/007908799/xsh/pthread_rwlock_rdlock.html:
	...
	A thread may hold multiple concurrent read locks on rwlock (that is,
	successfully call the pthread_rwlock_rdlock() function n times).
	...
	[EDEADLK]
	    The current thread already owns the read-write lock for writing.
	...

I noticed this when one of my tests failed.

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