From: Nicholas Piggin <npiggin@gmail•com>
To: linuxppc-dev@lists•ozlabs.org
Cc: Nicholas Piggin <npiggin@gmail•com>,
Benjamin Herrenschmidt <benh@kernel•crashing.org>
Subject: [PATCH 08/11] powerpc: allow soft-NMI watchdog to cover timer interrupts with large decrementers
Date: Sat, 5 May 2018 03:19:32 +1000 [thread overview]
Message-ID: <20180504171935.25410-9-npiggin@gmail.com> (raw)
In-Reply-To: <20180504171935.25410-1-npiggin@gmail.com>
Large decrementers (e.g., POWER9) can take a very long time to wrap,
so when the timer iterrupt handler sets the decrementer to max so as
to avoid taking another decrementer interrupt when hard enabling
interrupts before running timers, it effectively disables the soft
NMI coverage for timer interrupts.
Fix this by using the traditional 31-bit value instead, which wraps
after a few seconds. masked interrupt code does the same thing, and
in normal operation neither of these paths would ever wrap even the
31 bit value.
Note: the SMP watchdog should catch timer interrupt lockups, but it
is preferable for the local soft-NMI to catch them, mainly to avoid
the IPI.
Signed-off-by: Nicholas Piggin <npiggin@gmail•com>
---
arch/powerpc/kernel/time.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index ad876906f847..5862a3611795 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -578,22 +578,29 @@ void timer_interrupt(struct pt_regs *regs)
struct pt_regs *old_regs;
u64 now;
- /* Ensure a positive value is written to the decrementer, or else
- * some CPUs will continue to take decrementer exceptions.
- */
- set_dec(decrementer_max);
-
/* Some implementations of hotplug will get timer interrupts while
* offline, just ignore these and we also need to set
* decrementers_next_tb as MAX to make sure __check_irq_replay
* don't replay timer interrupt when return, otherwise we'll trap
* here infinitely :(
*/
- if (!cpu_online(smp_processor_id())) {
+ if (unlikely(!cpu_online(smp_processor_id()))) {
*next_tb = ~(u64)0;
+ set_dec(decrementer_max);
return;
}
+ /* Ensure a positive value is written to the decrementer, or else
+ * some CPUs will continue to take decrementer exceptions. When the
+ * PPC_WATCHDOG (decrementer based) is configured, keep this at most
+ * 31 bits, which is about 4 seconds on most systems, which gives
+ * the watchdog a chance of catching timer interrupt hard lockups.
+ */
+ if (IS_ENABLED(CONFIG_PPC_WATCHDOG))
+ set_dec(0x7fffffff);
+ else
+ set_dec(decrementer_max);
+
/* Conditionally hard-enable interrupts now that the DEC has been
* bumped to its maximum value
*/
--
2.17.0
next prev parent reply other threads:[~2018-05-04 17:20 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-04 17:19 [PATCH 00/11] assortment of timer, watchdog, interrupt Nicholas Piggin
2018-05-04 17:19 ` [PATCH 01/11] powerpc/64: irq_work avoid interrupt when called with hardware irqs enabled Nicholas Piggin
2018-06-04 14:10 ` [01/11] " Michael Ellerman
2018-05-04 17:19 ` [PATCH 02/11] powerpc/pseries: put cede MSR[EE] check under IRQ_SOFT_MASK_DEBUG Nicholas Piggin
2018-05-04 17:19 ` [PATCH 03/11] powerpc/64s: make PACA_IRQ_HARD_DIS track MSR[EE] closely Nicholas Piggin
2018-05-04 17:19 ` [PATCH 04/11] powerpc/64s: micro-optimise __hard_irq_enable() for mtmsrd L=1 support Nicholas Piggin
2018-05-04 17:19 ` [PATCH 05/11] powerpc/64: remove start_tb and accum_tb from thread_struct Nicholas Piggin
2018-05-04 17:19 ` [PATCH 06/11] powerpc/pseries: lparcfg calculate PURR on demand Nicholas Piggin
2018-05-04 17:19 ` [PATCH 07/11] powerpc: generic clockevents broadcast receiver call tick_receive_broadcast Nicholas Piggin
2018-05-05 14:38 ` kbuild test robot
2018-05-04 17:19 ` Nicholas Piggin [this message]
2018-05-04 17:19 ` [PATCH 09/11] powerpc: move timer broadcast code under GENERIC_CLOCKEVENTS_BROADCAST ifdef Nicholas Piggin
2018-05-04 17:19 ` [PATCH 10/11] powerpc: move a stray NMI IPI case under NMI_IPI ifdef Nicholas Piggin
2018-05-04 17:19 ` [PATCH 11/11] powerpc/time: account broadcast timer event interrupts separately Nicholas Piggin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180504171935.25410-9-npiggin@gmail.com \
--to=npiggin@gmail$(echo .)com \
--cc=benh@kernel$(echo .)crashing.org \
--cc=linuxppc-dev@lists$(echo .)ozlabs.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox