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Commit 09ac369c authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

clocksource: Add module refcount 



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

Signed-off-by: default avatarThomas 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: default avatarThomas Gleixner <tglx@linutronix.de>
parent ba919d1c

include/linux/clocksource.h

+3 −0
Original line number Diff line number Diff line
@@ -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;



/*

kernel/time/timekeeping.c

+14 −5
Original line number Diff line number Diff line
@@ -627,11 +627,20 @@ static int change_clocksource(void *data) 
	write_seqcount_begin(&timekeeper_seq);



	timekeeping_forward_now(tk);

	/*

	 * 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);