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Grammar tweaks for locking.9

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Reviewed by:	jhb
Approved by:	hrs (mentor)
This commit is contained in:
Benjamin Kaduk 2013-06-30 19:33:07 +00:00
parent f15ba03632
commit 10038699fb
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=252423
1 changed files with 13 additions and 12 deletions
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25
share/man/man9/locking.9
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@ -24,7 +24,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd May 22, 2013
.Dd June 30, 2013
.Dt LOCKING 9
.Os
.Sh NAME
@ -55,8 +55,7 @@ for details.
Spin mutexes are a variation of basic mutexes; the main difference between
the two is that spin mutexes never block.
Instead, they spin while waiting for the lock to be released.
Note that a thread that holds a spin mutex must never yield its CPU to
avoid deadlock.
To avoid deadlock, a thread that holds a spin mutex must never yield its CPU.
Unlike ordinary mutexes, spin mutexes disable interrupts when acquired.
Since disabling interrupts can be expensive, they are generally slower to
acquire and release.
@ -140,7 +139,7 @@ and in the buffer cache
They have features other lock types do not have such as sleep
timeouts, blocking upgrades,
writer starvation avoidance, draining, and an interlock mutex,
but this makes them complicated to both use and implement;
but this makes them complicated both to use and to implement;
for this reason, they should be avoided.
.Pp
See
@ -183,7 +182,7 @@ and
.Fn wakeup_one
also handle event-based thread blocking.
Unlike condition variables,
arbitrary addresses may be used as wait channels and an dedicated
arbitrary addresses may be used as wait channels and a dedicated
structure does not need to be allocated.
However, care must be taken to ensure that wait channel addresses are
unique to an event.
@ -280,21 +279,23 @@ they can and can not be combined.
Many of these rules are checked by
.Xr witness 4 .
.Ss Bounded vs. Unbounded Sleep
A bounded sleep
.Pq or blocking
is a sleep where the only resource needed to resume execution of a thread
In a bounded sleep
.Po also referred to as
.Dq blocking
.Pc
the only resource needed to resume execution of a thread
is CPU time for the owner of a lock that the thread is waiting to acquire.
An unbounded sleep
In an unbounded sleep
.Po
often referred to as simply
.Dq sleeping
.Pc
is a sleep where a thread is waiting for an external event or for a condition
a thread waits for an external event or for a condition
to become true.
In particular,
since there is always CPU time available,
a dependency chain of threads in bounded sleeps should always make forward
progress.
progress,
since there is always CPU time available.
This requires that no thread in a bounded sleep is waiting for a lock held
by a thread in an unbounded sleep.
To avoid priority inversions,