Add a module refcount, so the current clocksource cannot be removed
unconditionally.
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
---
include/linux/clocksource.h | 3 +++
kernel/time/timekeeping.c | 15 ++++++++++-----
2 files changed, 13 insertions(+), 5 deletions(-)
Index: tip/include/linux/clocksource.h
===================================================================
--- tip.orig/include/linux/clocksource.h
+++ tip/include/linux/clocksource.h
@@ -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 t
* @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
*/
struct clocksource {
/*
@@ -195,6 +197,7 @@ struct clocksource {
cycle_t cs_last;
cycle_t wd_last;
#endif
+ struct module *owner;
} ____cacheline_aligned;
/*
Index: tip/kernel/time/timekeeping.c
===================================================================
--- tip.orig/kernel/time/timekeeping.c
+++ tip/kernel/time/timekeeping.c
@@ -627,11 +627,16 @@ 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 (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);
--
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