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authorArnd Bergmann <arnd@arndb.de>2020-12-19 12:05:45 +0300
committerArnd Bergmann <arnd@arndb.de>2021-01-12 19:01:42 +0300
commit796130b1de29575e2e3fc3b0da4bda162b750db7 (patch)
tree0cd0887b05497c5a8f3a9c445ee1e20e179182b8 /arch/ia64
parent5c8fe583cce542aa0b84adc939ce85293de36e5e (diff)
downloadlinux-796130b1de29575e2e3fc3b0da4bda162b750db7.tar.xz
ia64: fix timer cleanup regression
A cleanup patch from my legacy timer series broke ia64 and led to RCU stall errors and a fast system clock: [ 909.360108] INFO: task systemd-sysv-ge:200 blocked for more than 127 seconds. [ 909.360108] Not tainted 5.10.0+ #130 [ 909.360108] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 909.360108] task:systemd-sysv-ge state:D stack: 0 pid: 200 ppid: 189 flags:0x00000000 [ 909.364108] [ 909.364108] Call Trace: [ 909.364423] [<a00000010109b210>] __schedule+0x890/0x21e0 [ 909.364423] sp=e0000100487d7b70 bsp=e0000100487d1748 [ 909.368423] [<a00000010109cc00>] schedule+0xa0/0x240 [ 909.368423] sp=e0000100487d7b90 bsp=e0000100487d16e0 [ 909.368558] [<a00000010109ce70>] io_schedule+0x70/0xa0 [ 909.368558] sp=e0000100487d7b90 bsp=e0000100487d16c0 [ 909.372290] [<a00000010109e1c0>] bit_wait_io+0x20/0xe0 [ 909.372290] sp=e0000100487d7b90 bsp=e0000100487d1698 [ 909.374168] rcu: INFO: rcu_sched detected stalls on CPUs/tasks: [ 909.376290] [<a00000010109d860>] __wait_on_bit+0xc0/0x1c0 [ 909.376290] sp=e0000100487d7b90 bsp=e0000100487d1648 [ 909.374168] rcu: 3-....: (2 ticks this GP) idle=19e/1/0x4000000000000002 softirq=1581/1581 fqs=2 [ 909.374168] (detected by 0, t=5661 jiffies, g=1089, q=3) [ 909.376290] [<a00000010109da80>] out_of_line_wait_on_bit+0x120/0x140 [ 909.376290] sp=e0000100487d7b90 bsp=e0000100487d1610 [ 909.374168] Task dump for CPU 3: [ 909.374168] task:khungtaskd state:R running task Revert most of my patch to make this work again, including the extra update_process_times()/profile_tick() and the local_irq_enable() in the loop that I expected not to be needed here. I have not found out exactly what goes wrong, and would suggest that someone with hardware access tries to convert this code into a singleshot clockevent driver, which should give better behavior in all cases. Reported-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de> Fixes: 2b49ddcef297 ("ia64: convert to legacy_timer_tick") Cc: John Stultz <john.stultz@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Stephen Boyd <sboyd@kernel.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'arch/ia64')
-rw-r--r--arch/ia64/kernel/time.c31
1 files changed, 18 insertions, 13 deletions
diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
index ed9fc3d057a6..43e8050145be 100644
--- a/arch/ia64/kernel/time.c
+++ b/arch/ia64/kernel/time.c
@@ -171,29 +171,34 @@ void vtime_account_hardirq(struct task_struct *tsk)
static irqreturn_t
timer_interrupt (int irq, void *dev_id)
{
- unsigned long cur_itm, new_itm, ticks;
+ unsigned long new_itm;
if (cpu_is_offline(smp_processor_id())) {
return IRQ_HANDLED;
}
new_itm = local_cpu_data->itm_next;
- cur_itm = ia64_get_itc();
- if (!time_after(cur_itm, new_itm)) {
+ if (!time_after(ia64_get_itc(), new_itm))
printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
- cur_itm, new_itm);
- ticks = 1;
- } else {
- ticks = DIV_ROUND_UP(cur_itm - new_itm,
- local_cpu_data->itm_delta);
- new_itm += ticks * local_cpu_data->itm_delta;
- }
+ ia64_get_itc(), new_itm);
+
+ while (1) {
+ new_itm += local_cpu_data->itm_delta;
+
+ legacy_timer_tick(smp_processor_id() == time_keeper_id);
- if (smp_processor_id() != time_keeper_id)
- ticks = 0;
+ local_cpu_data->itm_next = new_itm;
- legacy_timer_tick(ticks);
+ if (time_after(new_itm, ia64_get_itc()))
+ break;
+
+ /*
+ * Allow IPIs to interrupt the timer loop.
+ */
+ local_irq_enable();
+ local_irq_disable();
+ }
do {
/*