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futex.2: explanation of blocking behavior 

Shorten overlong sentence.
Highlight futex().
Tfix.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Heinrich Schuchardt 2015-03-29 20:48:20 +02:00 committed by Michael Kerrisk
parent 344df36631
commit b80daba225
1 changed files with 7 additions and 5 deletions
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man2/futex.2
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@ -59,16 +59,18 @@ in separate processes may be different,
the same physical address may be shared by the processes using
.BR mmap (2).)
When executing a futex operation that requests to block a thread,
When executing a
.BR futex ()
operation that requests to block a thread,
the kernel will only block if the futex word has the value that the
calling thread supplied as expected value.
The load from the futex word, the comparison with
the expected value,
and the actual blocking will happen atomically and totally
ordered with respect to concurrently executing futex operations
on the same futex word,
such as operations that wake threads blocked on this futex word.
Thus, the futex word is used to connect the synchronization in user spac
ordered with respect to concurrently executing
.BR futex ()
operations on the same futex word.
Thus, the futex word is used to connect the synchronization in user space
with the implementation of blocking by the kernel; similar to an atomic
compare-and-exchange operation that potentially changes shared memory,
blocking via a futex is an atomic compare-and-block operation.