[PATCH 04/24] timekeeping: Abort clocksource change in case of failure

Anna-Maria Behnsen
2024-09-11T13:30:03Z

From: Thomas Gleixner <tglx@linutronix.de>

There is no point to go through a full timekeeping update when acquiring a
module reference or enabling the new clocksource fails.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
---
kernel/time/timekeeping.c | 31 +++++++++++++------------------
1 file changed, 13 insertions(+), 18 deletions(-)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index bdc4a6fe040d..7b80dd70062c 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1577,33 +1577,29 @@ static void __timekeeping_set_tai_offset(struct timekeeper *tk, s32 tai_offset)
static int change_clocksource(void *data)
{
struct timekeeper *tk = &tk_core.timekeeper;
- struct clocksource *new, *old = NULL;
+ struct clocksource *new = data, *old = NULL;
unsigned long flags;
- bool change = false;
-
- new = (struct clocksource *) data;

/*
- * If the cs is in module, get a module reference. Succeeds
- * for built-in code (owner == NULL) as well.
+ * If the clocksource is in a module, get a module reference.
+ * Succeeds for built-in code (owner == NULL) as well. Abort if the
+ * reference can't be acquired.
*/
- if (try_module_get(new->owner)) {
- if (!new->enable || new->enable(new) == 0)
- change = true;
- else
- module_put(new->owner);
+ if (!try_module_get(new->owner))
+ return 0;
+
+ /* Abort if the device can't be enabled */
+ if (new->enable && new->enable(new) != 0) {
+ module_put(new->owner);
+ return 0;
}

raw_spin_lock_irqsave(&timekeeper_lock, flags);
write_seqcount_begin(&tk_core.seq);

timekeeping_forward_now(tk);
-
- if (change) {
- old = tk->tkr_mono.clock;
- tk_setup_internals(tk, new);
- }
-
+ old = tk->tkr_mono.clock;
+ tk_setup_internals(tk, new);
timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);

write_seqcount_end(&tk_core.seq);
@@ -1612,7 +1608,6 @@ static int change_clocksource(void *data)
if (old) {
if (old->disable)
old->disable(old);
-
module_put(old->owner);
}

--
2.39.2