diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 31b3a25680d08cfac3603d58b3d3783bbf1e34bb..763e96dcf8b18d9cf827c19084166f8073fc9119 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -679,12 +679,6 @@
loops can be debugged more effectively on production
systems.
- clocksource.max_cswd_read_retries= [KNL]
- Number of clocksource_watchdog() retries due to
- external delays before the clock will be marked
- unstable. Defaults to two retries, that is,
- three attempts to read the clock under test.
-
clocksource.verify_n_cpus= [KNL]
Limit the number of CPUs checked for clocksources
marked with CLOCK_SOURCE_VERIFY_PERCPU that
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 1d42d4b1732717056c4d7acca4ae311a3ca1cffc..0ad8b550bb4b4674fab70fc81dda94a76a7c9579 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -291,7 +291,19 @@ static inline void timer_probe(void) {}
#define TIMER_ACPI_DECLARE(name, table_id, fn) \
ACPI_DECLARE_PROBE_ENTRY(timer, name, table_id, 0, NULL, 0, fn)
-extern ulong max_cswd_read_retries;
+static inline unsigned int clocksource_get_max_watchdog_retry(void)
+{
+ /*
+ * When system is in the boot phase or under heavy workload, there
+ * can be random big latencies during the clocksource/watchdog
+ * read, so allow retries to filter the noise latency. As the
+ * latency's frequency and maximum value goes up with the number of
+ * CPUs, scale the number of retries with the number of online
+ * CPUs.
+ */
+ return (ilog2(num_online_cpus()) / 2) + 1;
+}
+
void clocksource_verify_percpu(struct clocksource *cs);
#endif /* _LINUX_CLOCKSOURCE_H */
diff --git a/kernel/time/clocksource-wdtest.c b/kernel/time/clocksource-wdtest.c
index df922f49d171baa2128005988faf80965b45ba25..d06185e054ea2173f273c826098cb04dde7dd05f 100644
--- a/kernel/time/clocksource-wdtest.c
+++ b/kernel/time/clocksource-wdtest.c
@@ -104,8 +104,8 @@ static void wdtest_ktime_clocksource_reset(void)
static int wdtest_func(void *arg)
{
unsigned long j1, j2;
+ int i, max_retries;
char *s;
- int i;
schedule_timeout_uninterruptible(holdoff * HZ);
@@ -139,18 +139,19 @@ static int wdtest_func(void *arg)
WARN_ON_ONCE(time_before(j2, j1 + NSEC_PER_USEC));
/* Verify tsc-like stability with various numbers of errors injected. */
- for (i = 0; i <= max_cswd_read_retries + 1; i++) {
- if (i <= 1 && i < max_cswd_read_retries)
+ max_retries = clocksource_get_max_watchdog_retry();
+ for (i = 0; i <= max_retries + 1; i++) {
+ if (i <= 1 && i < max_retries)
s = "";
- else if (i <= max_cswd_read_retries)
+ else if (i <= max_retries)
s = ", expect message";
else
s = ", expect clock skew";
- pr_info("--- Watchdog with %dx error injection, %lu retries%s.\n", i, max_cswd_read_retries, s);
+ pr_info("--- Watchdog with %dx error injection, %d retries%s.\n", i, max_retries, s);
WRITE_ONCE(wdtest_ktime_read_ndelays, i);
schedule_timeout_uninterruptible(2 * HZ);
WARN_ON_ONCE(READ_ONCE(wdtest_ktime_read_ndelays));
- WARN_ON_ONCE((i <= max_cswd_read_retries) !=
+ WARN_ON_ONCE((i <= max_retries) !=
!(clocksource_wdtest_ktime.flags & CLOCK_SOURCE_UNSTABLE));
wdtest_ktime_clocksource_reset();
}
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 4ef06651ad079f7bd28fb19cabfcb3b477dab53f..e5b260aa0e02c2de1293f8433280dd7122e14159 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -210,9 +210,6 @@ void clocksource_mark_unstable(struct clocksource *cs)
spin_unlock_irqrestore(&watchdog_lock, flags);
}
-ulong max_cswd_read_retries = 2;
-module_param(max_cswd_read_retries, ulong, 0644);
-EXPORT_SYMBOL_GPL(max_cswd_read_retries);
static int verify_n_cpus = 8;
module_param(verify_n_cpus, int, 0644);
@@ -224,11 +221,12 @@ enum wd_read_status {
static enum wd_read_status cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow)
{
- unsigned int nretries;
+ unsigned int nretries, max_retries;
u64 wd_end, wd_end2, wd_delta;
int64_t wd_delay, wd_seq_delay;
- for (nretries = 0; nretries <= max_cswd_read_retries; nretries++) {
+ max_retries = clocksource_get_max_watchdog_retry();
+ for (nretries = 0; nretries <= max_retries; nretries++) {
local_irq_disable();
*wdnow = watchdog->read(watchdog);
*csnow = cs->read(cs);
@@ -240,7 +238,7 @@ static enum wd_read_status cs_watchdog_read(struct clocksource *cs, u64 *csnow,
wd_delay = clocksource_cyc2ns(wd_delta, watchdog->mult,
watchdog->shift);
if (wd_delay <= WATCHDOG_MAX_SKEW) {
- if (nretries > 1 || nretries >= max_cswd_read_retries) {
+ if (nretries > 1 || nretries >= max_retries) {
pr_warn("timekeeping watchdog on CPU%d: %s retried %d times before success\n",
smp_processor_id(), watchdog->name, nretries);
}
diff --git a/tools/testing/selftests/rcutorture/bin/torture.sh b/tools/testing/selftests/rcutorture/bin/torture.sh
index d5a0d8a33c27bae242e8eb3f4e23ef67a576f24d..bbac5f4b03d04bfbda25da59a175cb09ca2f6fd2 100755
--- a/tools/testing/selftests/rcutorture/bin/torture.sh
+++ b/tools/testing/selftests/rcutorture/bin/torture.sh
@@ -567,7 +567,7 @@ then
torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 tsc=watchdog"
torture_set "clocksourcewd-1" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 45s --configs TREE03 --kconfig "CONFIG_TEST_CLOCKSOURCE_WATCHDOG=y" --trust-make
- torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 clocksource.max_cswd_read_retries=1 tsc=watchdog"
+ torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 tsc=watchdog"
torture_set "clocksourcewd-2" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 45s --configs TREE03 --kconfig "CONFIG_TEST_CLOCKSOURCE_WATCHDOG=y" --trust-make
# In case our work is already done...