pthread_rwlockattr_setkind_np.3: Clarify a PTHREAD_RWLOCK_PREFER_WRITER_NP detail

Clarify that it is recursive read locks on the read-write lock
that make it difficult to implement
PTHREAD_RWLOCK_PREFER_WRITER_NP.

Update the libc-alpha URL and provide the URL to the POSIX wording
that is quoted in the comment.

Reported-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Carlos O'Donell <carlos@redhat.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man3/pthread_rwlockattr_setkind_np.3 b/man3/pthread_rwlockattr_setkind_np.3
index b381972dc64dd53ed9f043e24c9f876aa77d4a50..a91c435520031b2cbaaa82f9abbbdc31a8ef1bad 100644 (file)
--- a/man3/pthread_rwlockattr_setkind_np.3
+++ b/man3/pthread_rwlockattr_setkind_np.3
@@ -80,7 +80,7 @@ starved.
 This is intended as the write lock analog of
 .BR PTHREAD_RWLOCK_PREFER_READER_NP .
 This is ignored by glibc because the POSIX requirement to support
-recursive writer locks would cause this option to create trivial
+recursive read locks would cause this option to create trivial
 deadlocks; instead use
 .B PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP
 which ensures the application developer will not take recursive
@@ -102,7 +102,8 @@ read locks thus avoiding deadlocks.
 .\" the writers to acquire and release the lock, and the writers will be
 .\" suspended waiting for every existing read lock to be released.
 .\" ---
-.\" http://sources.redhat.com/ml/libc-alpha/2000-01/msg00055.html
+.\" https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_rwlock_rdlock.html
+.\" https://sourceware.org/legacy-ml/libc-alpha/2000-01/msg00055.html
 .\" https://sourceware.org/bugzilla/show_bug.cgi?id=7057
 .TP
 .B PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP