[patch 5/8] time/timekeeping: Avoid invoking clock_was_set() twice

Thomas Gleixner
2021-04-27T08:40:10Z

do_adjtimex() might end up scheduling a delayed clock_was_set() via
timekeeping_advance() and then invoke clock_was_set() directly which is
pointless.

Make timekeeping_advance() return whether an invocation of clock_was_set()
is required and handle it at the call sites which allows do_adjtimex() to
issue a single direct call if required.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/time/timekeeping.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)

--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -2126,7 +2126,7 @@ static u64 logarithmic_accumulation(stru
* timekeeping_advance - Updates the timekeeper to the current time and
* current NTP tick length
*/
-static void timekeeping_advance(enum timekeeping_adv_mode mode)
+static bool timekeeping_advance(enum timekeeping_adv_mode mode)
{
struct timekeeper *real_tk = &tk_core.timekeeper;
struct timekeeper *tk = &shadow_timekeeper;
@@ -2197,9 +2197,8 @@ static void timekeeping_advance(enum tim
write_seqcount_end(&tk_core.seq);
out:
raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
- if (clock_set)
- /* Have to call _delayed version, since in irq context*/
- clock_was_set_delayed();
+
+ return !!clock_set;
}

/**
@@ -2208,7 +2207,8 @@ static void timekeeping_advance(enum tim
*/
void update_wall_time(void)
{
- timekeeping_advance(TK_ADV_TICK);
+ if (timekeeping_advance(TK_ADV_TICK))
+ clock_was_set_delayed();
}

/**
@@ -2388,8 +2388,9 @@ int do_adjtimex(struct __kernel_timex *t
{
struct timekeeper *tk = &tk_core.timekeeper;
struct audit_ntp_data ad;
- unsigned long flags;
+ bool clock_set = false;
struct timespec64 ts;
+ unsigned long flags;
s32 orig_tai, tai;
int ret;

@@ -2424,6 +2425,7 @@ int do_adjtimex(struct __kernel_timex *t
if (tai != orig_tai) {
__timekeeping_set_tai_offset(tk, tai);
timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
+ clock_set = true;
}
tk_update_leap_state(tk);

@@ -2434,9 +2436,9 @@ int do_adjtimex(struct __kernel_timex *t

/* Update the multiplier immediately if frequency was set directly */
if (txc->modes & (ADJ_FREQUENCY | ADJ_TICK))
- timekeeping_advance(TK_ADV_FREQ);
+ clock_set |= timekeeping_advance(TK_ADV_FREQ);

- if (tai != orig_tai)
+ if (clock_set)
clock_was_set();

ntp_notify_cmos_timer();