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Message-ID: <20220908195111.863334407@redhat.com>
Date: Thu, 08 Sep 2022 16:29:04 -0300
From: Marcelo Tosatti <mtosatti@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: Frederic Weisbecker <frederic@...nel.org>,
Juri Lelli <juri.lelli@...hat.com>,
Daniel Bristot de Oliveira <bristot@...nel.org>,
Prasad Pandit <ppandit@...hat.com>,
Valentin Schneider <vschneid@...hat.com>,
Yair Podemsky <ypodemsk@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Marcelo Tosatti <mtosatti@...hat.com>
Subject: [RFC PATCH 5/7] timekeeping_notify: use stop_machine_fail when appropriate
Change timekeeping_notify to use stop_machine_fail when appropriate,
which will fail in case the target CPU is tagged as block interference CPU.
Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
Index: linux-2.6/include/linux/clocksource.h
===================================================================
--- linux-2.6.orig/include/linux/clocksource.h
+++ linux-2.6/include/linux/clocksource.h
@@ -267,7 +267,7 @@ extern void clocksource_arch_init(struct
static inline void clocksource_arch_init(struct clocksource *cs) { }
#endif
-extern int timekeeping_notify(struct clocksource *clock);
+extern int timekeeping_notify(struct clocksource *clock, bool fail);
extern u64 clocksource_mmio_readl_up(struct clocksource *);
extern u64 clocksource_mmio_readl_down(struct clocksource *);
Index: linux-2.6/kernel/time/clocksource.c
===================================================================
--- linux-2.6.orig/kernel/time/clocksource.c
+++ linux-2.6/kernel/time/clocksource.c
@@ -117,7 +117,7 @@ static u64 suspend_start;
#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
static void clocksource_watchdog_work(struct work_struct *work);
-static void clocksource_select(void);
+static int clocksource_select(bool fail);
static LIST_HEAD(watchdog_list);
static struct clocksource *watchdog;
@@ -649,7 +649,7 @@ static int clocksource_watchdog_kthread(
{
mutex_lock(&clocksource_mutex);
if (__clocksource_watchdog_kthread())
- clocksource_select();
+ clocksource_select(false);
mutex_unlock(&clocksource_mutex);
return 0;
}
@@ -946,7 +946,7 @@ static struct clocksource *clocksource_f
return NULL;
}
-static void __clocksource_select(bool skipcur)
+static int __clocksource_select(bool skipcur, bool fail)
{
bool oneshot = tick_oneshot_mode_active();
struct clocksource *best, *cs;
@@ -954,7 +954,7 @@ static void __clocksource_select(bool sk
/* Find the best suitable clocksource */
best = clocksource_find_best(oneshot, skipcur);
if (!best)
- return;
+ return 0;
if (!strlen(override_name))
goto found;
@@ -991,10 +991,16 @@ static void __clocksource_select(bool sk
}
found:
- if (curr_clocksource != best && !timekeeping_notify(best)) {
+ if (curr_clocksource != best) {
+ int ret;
+
+ ret = timekeeping_notify(best, fail);
+ if (ret)
+ return ret;
pr_info("Switched to clocksource %s\n", best->name);
curr_clocksource = best;
}
+ return 0;
}
/**
@@ -1005,14 +1011,14 @@ found:
* Select the clocksource with the best rating, or the clocksource,
* which is selected by userspace override.
*/
-static void clocksource_select(void)
+static int clocksource_select(bool fail)
{
- __clocksource_select(false);
+ return __clocksource_select(false, fail);
}
-static void clocksource_select_fallback(void)
+static int clocksource_select_fallback(void)
{
- __clocksource_select(true);
+ return __clocksource_select(true, true);
}
/*
@@ -1031,7 +1037,7 @@ static int __init clocksource_done_booti
* Run the watchdog first to eliminate unstable clock sources
*/
__clocksource_watchdog_kthread();
- clocksource_select();
+ clocksource_select(false);
mutex_unlock(&clocksource_mutex);
return 0;
}
@@ -1179,7 +1185,7 @@ int __clocksource_register_scale(struct
clocksource_enqueue_watchdog(cs);
clocksource_watchdog_unlock(&flags);
- clocksource_select();
+ clocksource_select(false);
clocksource_select_watchdog(false);
__clocksource_suspend_select(cs);
mutex_unlock(&clocksource_mutex);
@@ -1208,7 +1214,7 @@ void clocksource_change_rating(struct cl
__clocksource_change_rating(cs, rating);
clocksource_watchdog_unlock(&flags);
- clocksource_select();
+ clocksource_select(false);
clocksource_select_watchdog(false);
clocksource_suspend_select(false);
mutex_unlock(&clocksource_mutex);
@@ -1230,8 +1236,12 @@ static int clocksource_unbind(struct clo
}
if (cs == curr_clocksource) {
+ int ret;
+
/* Select and try to install a replacement clock source */
- clocksource_select_fallback();
+ ret = clocksource_select_fallback();
+ if (ret)
+ return ret;
if (curr_clocksource == cs)
return -EBUSY;
}
@@ -1322,17 +1332,17 @@ static ssize_t current_clocksource_store
struct device_attribute *attr,
const char *buf, size_t count)
{
- ssize_t ret;
+ ssize_t ret, err;
mutex_lock(&clocksource_mutex);
ret = sysfs_get_uname(buf, override_name, count);
if (ret >= 0)
- clocksource_select();
+ err = clocksource_select(true);
mutex_unlock(&clocksource_mutex);
- return ret;
+ return err ? err : ret;
}
static DEVICE_ATTR_RW(current_clocksource);
Index: linux-2.6/kernel/time/timekeeping.c
===================================================================
--- linux-2.6.orig/kernel/time/timekeeping.c
+++ linux-2.6/kernel/time/timekeeping.c
@@ -13,6 +13,7 @@
#include <linux/sched.h>
#include <linux/sched/loadavg.h>
#include <linux/sched/clock.h>
+#include <linux/sched/isolation.h>
#include <linux/syscore_ops.h>
#include <linux/clocksource.h>
#include <linux/jiffies.h>
@@ -1497,13 +1498,24 @@ static int change_clocksource(void *data
* This function is called from clocksource.c after a new, better clock
* source has been registered. The caller holds the clocksource_mutex.
*/
-int timekeeping_notify(struct clocksource *clock)
+int timekeeping_notify(struct clocksource *clock, bool fail)
{
struct timekeeper *tk = &tk_core.timekeeper;
if (tk->tkr_mono.clock == clock)
return 0;
- stop_machine(change_clocksource, clock, NULL);
+
+ if (!fail)
+ stop_machine(change_clocksource, clock, NULL);
+ else {
+ int ret;
+
+ block_interf_read_lock();
+ ret = stop_machine_fail(change_clocksource, clock, NULL);
+ block_interf_read_unlock();
+ if (ret)
+ return ret;
+ }
tick_clock_notify();
return tk->tkr_mono.clock == clock ? 0 : -1;
}
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