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_umtx_op(2): Note deprecation of UMTX_OP_MUTEX_WAKE.

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This commit is contained in:
Jilles Tjoelker 2016-05-29 15:02:55 +00:00
parent 8e44e0ab19
commit 764be64b12
1 changed files with 15 additions and 1 deletions
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16
lib/libc/sys/_umtx_op.2
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@ -28,7 +28,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd May 17, 2016
.Dd May 29, 2016
.Dt _UMTX_OP 2
.Os
.Sh NAME
@ -1041,6 +1041,20 @@ with the byte addressed by the
if any.
Only normal mutexes are supported by the request.
The sleep queue is always one for a normal mutex type.
.Pp
This request is deprecated in favor of
.Dv UMTX_OP_MUTEX_WAKE2
since mutexes using it cannot synchronize their own destruction.
That is, the
.Dv m_owner
word has already been set to
.Dv UMUTEX_UNOWNED
when this request is made,
so that another thread can lock, unlock and destroy the mutex
(if no other thread uses the mutex afterwards).
Clearing the
.Dv UMUTEX_CONTESTED
bit may then modify freed memory.
.It Dv UMTX_OP_MUTEX_WAKE2
Check if a umutex is unlocked and wake up a waiter.
The arguments for the request are: