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For debugging purposes the condition varaibles keep track of the mutex used during a wait. The idea is to validate that all callers always use the same mutex. Unfortunately, we have seen cases where the caller reuses the condition variable with a different mutex but in a way which is known to be safe. My reading of the man pages suggests you should not do this and always cv_destroy()/cv_init() a new mutex. However, there is overhead in doing this and it does appear to be allowed under Solaris. To accomidate this behavior cv_wait_common() and __cv_timedwait() have been modified to clear the associated mutex when the last waiter is dropped. This ensures that while the condition variable is in use the incorrect mutex case is detected. It also allows the condition variable to be safely recycled without requiring the overhead of a cv_destroy()/cv_init() as long as it isn't currently in use. Finally, spin lock cv->cv_lock was removed because it is not required. When the condition variable is used properly the caller will always be holding the mutex so the spin lock is redundant. The lock was originally added because I expected to need to protect more than just the cv->cv_mutex. It turns out that was not the case. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
74 lines
2.8 KiB
C
74 lines
2.8 KiB
C
/*****************************************************************************\
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* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
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* Copyright (C) 2007 The Regents of the University of California.
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* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
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* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
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* UCRL-CODE-235197
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*
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* This file is part of the SPL, Solaris Porting Layer.
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* For details, see <http://github.com/behlendorf/spl/>.
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*
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* The SPL is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*
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* The SPL is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with the SPL. If not, see <http://www.gnu.org/licenses/>.
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\*****************************************************************************/
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#ifndef _SPL_CONDVAR_H
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#define _SPL_CONDVAR_H
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#include <linux/module.h>
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#include <linux/wait.h>
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#include <sys/kmem.h>
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#include <sys/mutex.h>
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/*
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* The kcondvar_t struct is protected by mutex taken externally before
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* calling any of the wait/signal funs, and passed into the wait funs.
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*/
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#define CV_MAGIC 0x346545f4
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#define CV_POISON 0x95
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typedef struct {
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int cv_magic;
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char *cv_name;
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int cv_name_size;
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wait_queue_head_t cv_event;
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atomic_t cv_waiters;
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kmutex_t *cv_mutex;
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} kcondvar_t;
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typedef enum { CV_DEFAULT=0, CV_DRIVER } kcv_type_t;
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extern void __cv_init(kcondvar_t *cvp, char *name, kcv_type_t type, void *arg);
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extern void __cv_destroy(kcondvar_t *cvp);
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extern void __cv_wait(kcondvar_t *cvp, kmutex_t *mp);
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extern void __cv_wait_interruptible(kcondvar_t *cvp, kmutex_t *mp);
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extern clock_t __cv_timedwait(kcondvar_t *cvp, kmutex_t *mp, clock_t exp_time);
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extern void __cv_signal(kcondvar_t *cvp);
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extern void __cv_broadcast(kcondvar_t *cvp);
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#define cv_init(cvp, name, type, arg) \
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({ \
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if ((name) == NULL) \
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__cv_init(cvp, #cvp, type, arg); \
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else \
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__cv_init(cvp, name, type, arg); \
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})
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#define cv_destroy(cvp) __cv_destroy(cvp)
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#define cv_wait(cvp, mp) __cv_wait(cvp, mp)
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#define cv_wait_interruptible(cvp, mp) __cv_wait_interruptible(cvp, mp)
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#define cv_timedwait(cvp, mp, t) __cv_timedwait(cvp, mp, t)
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#define cv_signal(cvp) __cv_signal(cvp)
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#define cv_broadcast(cvp) __cv_broadcast(cvp)
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#endif /* _SPL_CONDVAR_H */
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