Merge tip-468 branch

1 files changed, 9 insertions, 3 deletions

diff --git a/doc/Thread.3 b/doc/Thread.3
index 5966a71..2005c93 100644
--- a/doc/Thread.3
+++ b/doc/Thread.3
@@ -45,7 +45,9 @@ int
 .AP Tcl_Condition *condPtr in
 A condition variable, which must be associated with a mutex lock.
 .AP Tcl_Mutex *mutexPtr in
-A mutex lock.
+.VS TIP509
+A recursive mutex lock.
+.VE TIP509
 .AP "const Tcl_Time" *timePtr in
 A time limit on the condition wait.  NULL to wait forever.
 Note that a polling value of 0 seconds does not make much sense.
@@ -140,8 +142,12 @@ of code by calling \fBTcl_MutexLock\fR and \fBTcl_MutexUnlock\fR.
 If one thread holds a mutex, any other thread calling \fBTcl_MutexLock\fR will
 block until \fBTcl_MutexUnlock\fR is called.
 A mutex can be destroyed after its use by calling \fBTcl_MutexFinalize\fR.
-The result of locking a mutex twice from the same thread is undefined.
-On some platforms it will result in a deadlock.
+.VS TIP509
+Mutexes are reentrant: they can be locked several times from the same
+thread. However there must be exactly one call to
+\fBTcl_MutexUnlock\fR for each call to \fBTcl_MutexLock\fR in order
+for a thread to release a mutex completely.
+.VE TIP509
 The \fBTcl_MutexLock\fR, \fBTcl_MutexUnlock\fR and \fBTcl_MutexFinalize\fR
 procedures are defined as empty macros if not compiling with threads enabled.
 For declaration of mutexes the \fBTCL_DECLARE_MUTEX\fR macro should be used.