From 6881e75237a84093d0986f56223db3724619f26e Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 31 Jul 2024 12:23:51 +0200 Subject: tick/broadcast: Move per CPU pointer access into the atomic section The recent fix for making the take over of the broadcast timer more reliable retrieves a per CPU pointer in preemptible context. This went unnoticed as compilers hoist the access into the non-preemptible region where the pointer is actually used. But of course it's valid that the compiler keeps it at the place where the code puts it which rightfully triggers: BUG: using smp_processor_id() in preemptible [00000000] code: caller is hotplug_cpu__broadcast_tick_pull+0x1c/0xc0 Move it to the actual usage site which is in a non-preemptible region. Fixes: f7d43dd206e7 ("tick/broadcast: Make takeover of broadcast hrtimer reliable") Reported-by: David Wang <00107082@163.com> Signed-off-by: Thomas Gleixner Tested-by: Yu Liao Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/87ttg56ers.ffs@tglx --- kernel/time/tick-broadcast.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index b4843099a8da..ed58eebb4e8f 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -1141,7 +1141,6 @@ void tick_broadcast_switch_to_oneshot(void) #ifdef CONFIG_HOTPLUG_CPU void hotplug_cpu__broadcast_tick_pull(int deadcpu) { - struct tick_device *td = this_cpu_ptr(&tick_cpu_device); struct clock_event_device *bc; unsigned long flags; @@ -1167,6 +1166,8 @@ void hotplug_cpu__broadcast_tick_pull(int deadcpu) * device to avoid the starvation. */ if (tick_check_broadcast_expired()) { + struct tick_device *td = this_cpu_ptr(&tick_cpu_device); + cpumask_clear_cpu(smp_processor_id(), tick_broadcast_force_mask); tick_program_event(td->evtdev->next_event, 1); } -- cgit v1.2.3 From f2655ac2c06a15558e51ed6529de280e1553c86e Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 2 Aug 2024 08:46:15 -0700 Subject: clocksource: Fix brown-bag boolean thinko in cs_watchdog_read() The current "nretries > 1 || nretries >= max_retries" check in cs_watchdog_read() will always evaluate to true, and thus pr_warn(), if nretries is greater than 1. The intent is instead to never warn on the first try, but otherwise warn if the successful retry was the last retry. Therefore, change that "||" to "&&". Fixes: db3a34e17433 ("clocksource: Retry clock read if long delays detected") Reported-by: Borislav Petkov Signed-off-by: Paul E. McKenney Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/20240802154618.4149953-2-paulmck@kernel.org --- kernel/time/clocksource.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index d25ba49e313c..d0538a75f4c6 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -246,7 +246,7 @@ static enum wd_read_status cs_watchdog_read(struct clocksource *cs, u64 *csnow, wd_delay = cycles_to_nsec_safe(watchdog, *wdnow, wd_end); if (wd_delay <= WATCHDOG_MAX_SKEW) { - if (nretries > 1 || nretries >= max_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); } -- cgit v1.2.3