X-Git-Url: https://gerrit.opnfv.org/gerrit/gitweb?a=blobdiff_plain;f=kernel%2Fdrivers%2Fstaging%2Funisys%2Fvisorutil%2Fperiodic_work.c;fp=kernel%2Fdrivers%2Fstaging%2Funisys%2Fvisorutil%2Fperiodic_work.c;h=abbfb48894f309e5405f9d7ae2ab3751786bc956;hb=9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00;hp=0000000000000000000000000000000000000000;hpb=98260f3884f4a202f9ca5eabed40b1354c489b29;p=kvmfornfv.git diff --git a/kernel/drivers/staging/unisys/visorutil/periodic_work.c b/kernel/drivers/staging/unisys/visorutil/periodic_work.c new file mode 100644 index 000000000..abbfb4889 --- /dev/null +++ b/kernel/drivers/staging/unisys/visorutil/periodic_work.c @@ -0,0 +1,204 @@ +/* periodic_work.c + * + * Copyright (C) 2010 - 2013 UNISYS CORPORATION + * All rights reserved. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or (at + * your option) any later version. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or + * NON INFRINGEMENT. See the GNU General Public License for more + * details. + */ + +/* + * Helper functions to schedule periodic work in Linux kernel mode. + */ + +#include "timskmod.h" +#include "periodic_work.h" + +#define MYDRVNAME "periodic_work" + +struct periodic_work { + rwlock_t lock; + struct delayed_work work; + void (*workfunc)(void *); + void *workfuncarg; + BOOL is_scheduled; + BOOL want_to_stop; + ulong jiffy_interval; + struct workqueue_struct *workqueue; + const char *devnam; +}; + +static void periodic_work_func(struct work_struct *work) +{ + struct periodic_work *pw; + + pw = container_of(work, struct periodic_work, work.work); + (*pw->workfunc)(pw->workfuncarg); +} + +struct periodic_work *visor_periodic_work_create(ulong jiffy_interval, + struct workqueue_struct *workqueue, + void (*workfunc)(void *), + void *workfuncarg, + const char *devnam) +{ + struct periodic_work *pw; + + pw = kzalloc(sizeof(*pw), GFP_KERNEL | __GFP_NORETRY); + if (!pw) + return NULL; + + rwlock_init(&pw->lock); + pw->jiffy_interval = jiffy_interval; + pw->workqueue = workqueue; + pw->workfunc = workfunc; + pw->workfuncarg = workfuncarg; + pw->devnam = devnam; + return pw; +} +EXPORT_SYMBOL_GPL(visor_periodic_work_create); + +void visor_periodic_work_destroy(struct periodic_work *pw) +{ + kfree(pw); +} +EXPORT_SYMBOL_GPL(visor_periodic_work_destroy); + +/** Call this from your periodic work worker function to schedule the next + * call. + * If this function returns FALSE, there was a failure and the + * periodic work is no longer scheduled + */ +BOOL visor_periodic_work_nextperiod(struct periodic_work *pw) +{ + BOOL rc = FALSE; + + write_lock(&pw->lock); + if (pw->want_to_stop) { + pw->is_scheduled = FALSE; + pw->want_to_stop = FALSE; + rc = TRUE; /* yes, TRUE; see visor_periodic_work_stop() */ + goto unlock; + } else if (queue_delayed_work(pw->workqueue, &pw->work, + pw->jiffy_interval) < 0) { + pw->is_scheduled = FALSE; + rc = FALSE; + goto unlock; + } + rc = TRUE; +unlock: + write_unlock(&pw->lock); + return rc; +} +EXPORT_SYMBOL_GPL(visor_periodic_work_nextperiod); + +/** This function returns TRUE iff new periodic work was actually started. + * If this function returns FALSE, then no work was started + * (either because it was already started, or because of a failure). + */ +BOOL visor_periodic_work_start(struct periodic_work *pw) +{ + BOOL rc = FALSE; + + write_lock(&pw->lock); + if (pw->is_scheduled) { + rc = FALSE; + goto unlock; + } + if (pw->want_to_stop) { + rc = FALSE; + goto unlock; + } + INIT_DELAYED_WORK(&pw->work, &periodic_work_func); + if (queue_delayed_work(pw->workqueue, &pw->work, + pw->jiffy_interval) < 0) { + rc = FALSE; + goto unlock; + } + pw->is_scheduled = TRUE; + rc = TRUE; +unlock: + write_unlock(&pw->lock); + return rc; +} +EXPORT_SYMBOL_GPL(visor_periodic_work_start); + +/** This function returns TRUE iff your call actually stopped the periodic + * work. + * + * -- PAY ATTENTION... this is important -- + * + * NO NO #1 + * + * Do NOT call this function from some function that is running on the + * same workqueue as the work you are trying to stop might be running + * on! If you violate this rule, visor_periodic_work_stop() MIGHT work, + * but it also MIGHT get hung up in an infinite loop saying + * "waiting for delayed work...". This will happen if the delayed work + * you are trying to cancel has been put in the workqueue list, but can't + * run yet because we are running that same workqueue thread right now. + * + * Bottom line: If you need to call visor_periodic_work_stop() from a + * workitem, be sure the workitem is on a DIFFERENT workqueue than the + * workitem that you are trying to cancel. + * + * If I could figure out some way to check for this "no no" condition in + * the code, I would. It would have saved me the trouble of writing this + * long comment. And also, don't think this is some "theoretical" race + * condition. It is REAL, as I have spent the day chasing it. + * + * NO NO #2 + * + * Take close note of the locks that you own when you call this function. + * You must NOT own any locks that are needed by the periodic work + * function that is currently installed. If you DO, a deadlock may result, + * because stopping the periodic work often involves waiting for the last + * iteration of the periodic work function to complete. Again, if you hit + * this deadlock, you will get hung up in an infinite loop saying + * "waiting for delayed work...". + */ +BOOL visor_periodic_work_stop(struct periodic_work *pw) +{ + BOOL stopped_something = FALSE; + + write_lock(&pw->lock); + stopped_something = pw->is_scheduled && (!pw->want_to_stop); + while (pw->is_scheduled) { + pw->want_to_stop = TRUE; + if (cancel_delayed_work(&pw->work)) { + /* We get here if the delayed work was pending as + * delayed work, but was NOT run. + */ + WARN_ON(!pw->is_scheduled); + pw->is_scheduled = FALSE; + } else { + /* If we get here, either the delayed work: + * - was run, OR, + * - is running RIGHT NOW on another processor, OR, + * - wasn't even scheduled (there is a miniscule + * timing window where this could be the case) + * flush_workqueue() would make sure it is finished + * executing, but that still isn't very useful, which + * explains the loop... + */ + } + if (pw->is_scheduled) { + write_unlock(&pw->lock); + SLEEPJIFFIES(10); + write_lock(&pw->lock); + } else { + pw->want_to_stop = FALSE; + } + } + write_unlock(&pw->lock); + return stopped_something; +} +EXPORT_SYMBOL_GPL(visor_periodic_work_stop);