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clocksource: Add module refcount 

Add a module refcount, so the current clocksource cannot be removed
unconditionally.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130425143435.762417789@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
hifive-unleashed-5.1
Thomas Gleixner 2013-04-25 20:31:44 +00:00
parent ba919d1caa
commit 09ac369c82
2 changed files with 17 additions and 5 deletions
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3
include/linux/clocksource.h
View File

@ -21,6 +21,7 @@
/* clocksource cycle base type */
typedef u64 cycle_t;
struct clocksource;
struct module;
#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
#include <asm/clocksource.h>
@ -162,6 +163,7 @@ extern u64 timecounter_cyc2time(struct timecounter *tc,
* @suspend: suspend function for the clocksource, if necessary
* @resume: resume function for the clocksource, if necessary
* @cycle_last: most recent cycle counter value seen by ::read()
* @owner: module reference, must be set by clocksource in modules
*/
struct clocksource {
/*
@ -195,6 +197,7 @@ struct clocksource {
cycle_t cs_last;
cycle_t wd_last;
#endif
struct module *owner;
} ____cacheline_aligned;
/*

19
kernel/time/timekeeping.c
View File

@ -627,11 +627,20 @@ static int change_clocksource(void *data)
write_seqcount_begin(&timekeeper_seq);
timekeeping_forward_now(tk);
if (!new->enable || new->enable(new) == 0) {
old = tk->clock;
tk_setup_internals(tk, new);
if (old->disable)
old->disable(old);
/*
* If the cs is in module, get a module reference. Succeeds
* for built-in code (owner == NULL) as well.
*/
if (try_module_get(new->owner)) {
if (!new->enable || new->enable(new) == 0) {
old = tk->clock;
tk_setup_internals(tk, new);
if (old->disable)
old->disable(old);
module_put(old->owner);
} else {
module_put(new->owner);
}
}
timekeeping_update(tk, true, true);