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Revert "clocksource: Avoid accidental unstable marking of clocksources"

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This reverts commit fd99aeb978 which is
commit c86ff8c55b upstream.

It breaks the Android kernel ABI and is not an issue for Android
systems, so revert it.

Bug: 161946584
Fixes: fd99aeb978 ("clocksource: Avoid accidental unstable marking of clocksources")
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I6ea81231f082921f85c3c671f120724a40a191fe
This commit is contained in:
Greg Kroah-Hartman
2022-01-31 18:08:29 +01:00
parent 4ec3c2eea5
commit fae0741a78
1 changed files with 9 additions and 41 deletions
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50
kernel/time/clocksource.c
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@@ -105,7 +105,7 @@ static u64 suspend_start;
* This delay could be due to SMIs, NMIs, or to VCPU preemptions. Used as
* a lower bound for cs->uncertainty_margin values when registering clocks.
*/
#define WATCHDOG_MAX_SKEW (100 * NSEC_PER_USEC)
#define WATCHDOG_MAX_SKEW (50 * NSEC_PER_USEC)
#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
static void clocksource_watchdog_work(struct work_struct *work);
@@ -200,24 +200,17 @@ void clocksource_mark_unstable(struct clocksource *cs)
static ulong max_cswd_read_retries = 3;
module_param(max_cswd_read_retries, ulong, 0644);
enum wd_read_status {
WD_READ_SUCCESS,
WD_READ_UNSTABLE,
WD_READ_SKIP
};
static enum wd_read_status cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow)
static bool cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow)
{
unsigned int nretries;
u64 wd_end, wd_end2, wd_delta;
int64_t wd_delay, wd_seq_delay;
u64 wd_end, wd_delta;
int64_t wd_delay;
for (nretries = 0; nretries <= max_cswd_read_retries; nretries++) {
local_irq_disable();
*wdnow = watchdog->read(watchdog);
*csnow = cs->read(cs);
wd_end = watchdog->read(watchdog);
wd_end2 = watchdog->read(watchdog);
local_irq_enable();
wd_delta = clocksource_delta(wd_end, *wdnow, watchdog->mask);
@@ -228,34 +221,13 @@ static enum wd_read_status cs_watchdog_read(struct clocksource *cs, u64 *csnow,
pr_warn("timekeeping watchdog on CPU%d: %s retried %d times before success\n",
smp_processor_id(), watchdog->name, nretries);
}
return WD_READ_SUCCESS;
return true;
}
/*
* Now compute delay in consecutive watchdog read to see if
* there is too much external interferences that cause
* significant delay in reading both clocksource and watchdog.
*
* If consecutive WD read-back delay > WATCHDOG_MAX_SKEW/2,
* report system busy, reinit the watchdog and skip the current
* watchdog test.
*/
wd_delta = clocksource_delta(wd_end2, wd_end, watchdog->mask);
wd_seq_delay = clocksource_cyc2ns(wd_delta, watchdog->mult, watchdog->shift);
if (wd_seq_delay > WATCHDOG_MAX_SKEW/2)
goto skip_test;
}
pr_warn("timekeeping watchdog on CPU%d: %s read-back delay of %lldns, attempt %d, marking unstable\n",
smp_processor_id(), watchdog->name, wd_delay, nretries);
return WD_READ_UNSTABLE;
skip_test:
pr_info("timekeeping watchdog on CPU%d: %s wd-wd read-back delay of %lldns\n",
smp_processor_id(), watchdog->name, wd_seq_delay);
pr_info("wd-%s-wd read-back delay of %lldns, clock-skew test skipped!\n",
cs->name, wd_delay);
return WD_READ_SKIP;
return false;
}
static u64 csnow_mid;
@@ -318,7 +290,6 @@ static void clocksource_watchdog(struct timer_list *unused)
int next_cpu, reset_pending;
int64_t wd_nsec, cs_nsec;
struct clocksource *cs;
enum wd_read_status read_ret;
u32 md;
spin_lock(&watchdog_lock);
@@ -336,12 +307,9 @@ static void clocksource_watchdog(struct timer_list *unused)
continue;
}
read_ret = cs_watchdog_read(cs, &csnow, &wdnow);
if (read_ret != WD_READ_SUCCESS) {
if (read_ret == WD_READ_UNSTABLE)
/* Clock readout unreliable, so give it up. */
__clocksource_unstable(cs);
if (!cs_watchdog_read(cs, &csnow, &wdnow)) {
/* Clock readout unreliable, so give it up. */
__clocksource_unstable(cs);
continue;
}