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Update comments to mention that each turnstile contains two queues and to

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describe turnstile_disown() and turnstile_empty().
This commit is contained in:
John Baldwin 2006-04-18 18:21:38 +00:00
parent f1a4b852dc
commit 62375b03cd
1 changed files with 11 additions and 4 deletions
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15
sys/sys/turnstile.h
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@ -34,7 +34,10 @@
/*
* Turnstile interface. Non-sleepable locks use a turnstile for the
* queue of threads blocked on them when they are contested.
* queue of threads blocked on them when they are contested. Each
* turnstile contains two sub-queues: one for threads waiting for a
* shared, or eread, lock, and one for threads waiting for an
* exclusive, or write, lock.
*
* A thread calls turnstile_lock() to lock the turnstile chain associated
* with a given lock. A thread calls turnstile_wait() when the lock is
@ -50,7 +53,10 @@
* blocked threads. The turnstile_signal() function returns true if the
* turnstile became empty as a result. After the higher level code finishes
* releasing the lock, turnstile_unpend() must be called to wake up the
* pending thread(s).
* pending thread(s) and give up ownership of the turnstile.
*
* Alternatively, if a thread wishes to relinquish ownership of a thread
* without waking up any waiters, it may call turnstile_disown().
*
* When a lock is acquired that already has at least one thread contested
* on it, the new owner of the lock must claim ownership of the turnstile
@ -62,8 +68,9 @@
* released at thread destruction may not be the same turnstile that the
* thread allocated when it was created.
*
* The highest priority thread blocked on a turnstile can be obtained via
* turnstile_head().
* The highest priority thread blocked on a specified queue of a
* turnstile can be obtained via turnstile_head(). A given queue can
* also be queried to see if it is empty via turnstile_empty().
*/
struct lock_object;