linux-stable.git/arch/powerpc/kernel/time.c, branch v6.2

powerpc/64: Fix perf profiling asynchronous interrupt handlers

2023-01-30T09:07:42+00:00

Interrupt entry sets the soft mask to IRQS_ALL_DISABLED to match the
hard irq disabled state. So when should_hard_irq_enable() returns true
because we want PMI interrupts in irq handlers, MSR[EE] is enabled but
PMIs just get soft-masked. Fix this by clearing IRQS_PMI_DISABLED before
enabling MSR[EE].

This also tidies some of the warnings, no need to duplicate them in
both should_hard_irq_enable() and do_hard_irq_enable().

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20230121100156.2824054-1-npiggin@gmail.com

powerpc: remove the last remnants of cputime_t

2022-11-24T12:31:48+00:00

cputime_t was a core kernel type, removed by commits
ed5c8c854f2b..b672592f0221. As explained in commit b672592f0221
("sched/cputime: Remove generic asm headers"), the final cleanup
is for the arch to provide cputime_to_nsec[s](). Commit ade7667a981b
("powerpc: Add cputime_to_nsecs()") did that, but justdidn't remove
the then-unused cputime_to_usecs(), cputime_t type, and associated
remnants.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20221006105653.115829-1-npiggin@gmail.com

powerpc/time: avoid programming DEC at the start of the timer interrupt

2022-09-28T09:22:09+00:00

Setting DEC to maximum at the start of the timer interrupt is not
necessary and can be avoided for performance when MSR[EE] is not
enabled during the handler as explained in commit 0faf20a1ad16
("powerpc/64s/interrupt: Don't enable MSR[EE] in irq handlers unless
perf is in use"), where this change was first attempted.

The idea is that the timer interrupt runs with MSR[EE]=0, and at the end
of the interrupt DEC is programmed to the next timer interval, so there
is no need to clear the decrementer exception before then.

When the above commit was merged, that was not quite true. The low res
timer subsystem had some cases in the oneshot timer code where if the
tick was to be stopped and no timers active, the clock device would not
get the ->set_state_oneshot_stopped() call, so DEC would not get
reprogrammed, and this would hang taking continual timer interrupts.

So this was reverted in commit d2b9be1f4af5 ("powerpc/time: Always set
decrementer in timer_interrupt()"), which was a partial revert of the
above commit.

Commit 62c1256d5447 ("timers/nohz: Switch to ONESHOT_STOPPED in the
low-res handler when the tick is stopped") was later merged to fix this
missing case in the timer subsystem, so now the behaviour can be
restored.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20220909142457.278032-1-npiggin@gmail.com

powerpc/pseries: Move dtl scanning and steal time accounting to pseries platform

2022-09-05T04:14:27+00:00

dtl is the PAPR Dispatch Trace Log, which is entirely a pseries feature.
The pseries platform alrady has a file dealing with the dtl, so move
scanning for stolen time accounting there from kernel/time.c.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20220902085316.2071519-5-npiggin@gmail.com

powerpc: Add missing headers

2022-05-08T12:15:40+00:00

Don't inherit headers "by chances" from asm/prom.h, asm/mpc52xx.h,
asm/pci.h etc...

Include the needed headers, and remove asm/prom.h when it was
needed exclusively for pulling necessary headers.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/be8bdc934d152a7d8ee8d1a840d5596e2f7d85e0.1646767214.git.christophe.leroy@csgroup.eu

powerpc: fix typos in comments

2022-05-05T12:12:44+00:00

Various spelling mistakes in comments.
Detected with the help of Coccinelle.

Signed-off-by: Julia Lawall 
Reviewed-by: Joel Stanley 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20220430185654.5855-1-Julia.Lawall@inria.fr

Merge tag 'v5.18-rc4' into next

2022-05-05T12:09:35+00:00

Merge master into next, to bring in commit 5f24d5a579d1 ("mm, hugetlb:
allow for "high" userspace addresses"), which is needed as a
prerequisite for the series converting powerpc to the generic mmap
logic.

powerpc/time: Fix sparse warnings

2022-05-04T09:37:42+00:00

We found these warnings in arch/powerpc/kernel/time.c as follows:
  warning: symbol 'decrementer_max' was not declared. Should it be static?
  warning: symbol 'rtc_lock' was not declared. Should it be static?
  warning: symbol 'dtl_consumer' was not declared. Should it be static?

Declare 'decrementer_max' in powerpc asm/time.h.

Include linux/mc146818rtc.h in powerpc kernel/time.c where 'rtc_lock' is
declared. And remove duplicated declaration of 'rtc_lock' in powerpc
platforms/chrp/time.c because it has included linux/mc146818rtc.h.

Move 'dtl_consumer' definition after "include " because it is
declared there.

Reported-by: Hulk Robot 
Signed-off-by: He Ying 
Reviewed-by: Christophe Leroy 
Reviewed-by: Alexandre Belloni 
Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210324090939.143477-1-heying24@huawei.com

powerpc/time: Always set decrementer in timer_interrupt()

2022-04-21T06:10:56+00:00

This is a partial revert of commit 0faf20a1ad16 ("powerpc/64s/interrupt:
Don't enable MSR[EE] in irq handlers unless perf is in use").

Prior to that commit, we always set the decrementer in
timer_interrupt(), to clear the timer interrupt. Otherwise we could end
up continuously taking timer interrupts.

When high res timers are enabled there is no problem seen with leaving
the decrementer untouched in timer_interrupt(), because it will be
programmed via hrtimer_interrupt() -> tick_program_event() ->
clockevents_program_event() -> decrementer_set_next_event().

However with CONFIG_HIGH_RES_TIMERS=n or booting with highres=off, we
see a stall/lockup, because tick_nohz_handler() does not cause a
reprogram of the decrementer, leading to endless timer interrupts.
Example trace:

  [    1.898617][    T7] Freeing initrd memory: 2624K^M
  [   22.680919][    C1] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:^M
  [   22.682281][    C1] rcu:     0-....: (25 ticks this GP) idle=073/0/0x1 softirq=10/16 fqs=1050 ^M
  [   22.682851][    C1]  (detected by 1, t=2102 jiffies, g=-1179, q=476)^M
  [   22.683649][    C1] Sending NMI from CPU 1 to CPUs 0:^M
  [   22.685252][    C0] NMI backtrace for cpu 0^M
  [   22.685649][    C0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.16.0-rc2-00185-g0faf20a1ad16 #145^M
  [   22.686393][    C0] NIP:  c000000000016d64 LR: c000000000f6cca4 CTR: c00000000019c6e0^M
  [   22.686774][    C0] REGS: c000000002833590 TRAP: 0500   Not tainted  (5.16.0-rc2-00185-g0faf20a1ad16)^M
  [   22.687222][    C0] MSR:  8000000000009033   CR: 24000222  XER: 00000000^M
  [   22.688297][    C0] CFAR: c00000000000c854 IRQMASK: 0 ^M
  ...
  [   22.692637][    C0] NIP [c000000000016d64] arch_local_irq_restore+0x174/0x250^M
  [   22.694443][    C0] LR [c000000000f6cca4] __do_softirq+0xe4/0x3dc^M
  [   22.695762][    C0] Call Trace:^M
  [   22.696050][    C0] [c000000002833830] [c000000000f6cc80] __do_softirq+0xc0/0x3dc (unreliable)^M
  [   22.697377][    C0] [c000000002833920] [c000000000151508] __irq_exit_rcu+0xd8/0x130^M
  [   22.698739][    C0] [c000000002833950] [c000000000151730] irq_exit+0x20/0x40^M
  [   22.699938][    C0] [c000000002833970] [c000000000027f40] timer_interrupt+0x270/0x460^M
  [   22.701119][    C0] [c0000000028339d0] [c0000000000099a8] decrementer_common_virt+0x208/0x210^M

Possibly this should be fixed in the lowres timing code, but that would
be a generic change and could take some time and may not backport
easily, so for now make the programming of the decrementer unconditional
again in timer_interrupt() to avoid the stall/lockup.

Fixes: 0faf20a1ad16 ("powerpc/64s/interrupt: Don't enable MSR[EE] in irq handlers unless perf is in use")
Reported-by: Miguel Ojeda 
Signed-off-by: Michael Ellerman 
Reviewed-by: Nicholas Piggin 
Link: https://lore.kernel.org/r/20220420141657.771442-1-mpe@ellerman.id.au

powerpc/time: improve decrementer clockevent processing

2022-03-16T05:55:23+00:00

The stop/shutdown op should not use decrementer_set_next_event because
that sets decrementers_next_tb to now + decrementer_max, which means a
decrementer interrupt that occurs after that time will call the
clockevent event handler unexpectedly. Set next_tb to ~0 here to prevent
any clock event call. Init all clockevents to stopped.

Then the decrementer clockevent device always has event_handler set and
applicable because we know the clock event device was not stopped. So
make this call unconditional to show that it is always called. next_tb
need not be set to ~0 before the event handler is called because it will
stop the clockevent device if there is no other timer.

Finally, the timer broadcast interrupt should not modify next_tb because
it is not involved with the local decrementer clockevent on this CPU.

This doesn't fix a known bug, just tidies the code.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20220124143930.3923442-3-npiggin@gmail.com