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d599e4fa79
Previously we would ASSERT in cv_destroy() if it was ever called with active waiters. However, I've now seen several instances in OpenSolaris code where they do the following: cv_broadcast(); cv_destroy(); This leaves no time for active waiters to be woken up and scheduled and we trip the ASSERT. This has not been observed to be an issue on OpenSolaris because their cv_destroy() basically does nothing. They still do run the risk of the memory being free'd after the cv_destroy() and hitting a bad paging request. But in practice this race is so small and unlikely it either doesn't happen, or is so unlikely when it does happen the root cause has not yet been identified. Rather than risk the same issue in our code this change updates cv_destroy() to block until all waiters have been woken and scheduled. This may take some time because each waiter must acquire the mutex. This change may have an impact on performance for frequently created and destroyed condition variables. That however is a price worth paying it avoid crashing your system. If performance issues are observed they can be addressed by the caller.
79 lines
3.1 KiB
C
79 lines
3.1 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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wait_queue_head_t cv_destroy;
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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 clock_t __cv_timedwait_interruptible(kcondvar_t *cvp, kmutex_t *mp,
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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_timedwait_interruptible(cvp, mp, t) \
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__cv_timedwait_interruptible(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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