linux-kernel - [PATCH v12 2/7] arm64: idle: Tag the arm64 idle functions as _

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Message-ID: <20230830121115.v12.2.I4baba13e220bdd24d11400c67f137c35f07f82c7@changeid>
Date:   Wed, 30 Aug 2023 12:11:23 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Sumit Garg <sumit.garg@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Marc Zyngier <maz@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Masayoshi Mizuma <msys.mizuma@...il.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Lecopzer Chen <lecopzer.chen@...iatek.com>,
        Tomohiro Misono <misono.tomohiro@...itsu.com>,
        Stephane Eranian <eranian@...gle.com>,
        kgdb-bugreport@...ts.sourceforge.net,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <swboyd@...omium.org>, ito-yuichi@...itsu.com,
        linux-perf-users@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
        Douglas Anderson <dianders@...omium.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH v12 2/7] arm64: idle: Tag the arm64 idle functions as __cpuidle

As per the (somewhat recent) comment before the definition of
`__cpuidle`, the tag is like `noinstr` but also marks a function so it
can be identified by cpu_in_idle(). Let's add these markings to arm64
cpuidle functions

With this change we get useful backtraces like:

  NMI backtrace for cpu N skipped: idling at cpu_do_idle+0x94/0x98

instead of useless backtraces when dumping all processors using
nmi_cpu_backtrace().

NOTE: this patch won't make cpu_in_idle() work perfectly for arm64,
but it doesn't hurt and does catch some cases. Specifically an example
that wasn't caught in my testing looked like this:

 gic_cpu_sys_reg_init+0x1f8/0x314
 gic_cpu_pm_notifier+0x40/0x78
 raw_notifier_call_chain+0x5c/0x134
 cpu_pm_notify+0x38/0x64
 cpu_pm_exit+0x20/0x2c
 psci_enter_idle_state+0x48/0x70
 cpuidle_enter_state+0xb8/0x260
 cpuidle_enter+0x44/0x5c
 do_idle+0x188/0x30c

Acked-by: Mark Rutland <mark.rutland@....com>
Reviewed-by: Stephen Boyd <swboyd@...omium.org>
Acked-by: Sumit Garg <sumit.garg@...aro.org>
Signed-off-by: Douglas Anderson <dianders@...omium.org>
---

(no changes since v11)

Changes in v11:
- Updated commit message as per Stephen.

Changes in v9:
- Added to commit message that this doesn't catch all cases.

Changes in v8:
- "Tag the arm64 idle functions as __cpuidle" new for v8

 arch/arm64/kernel/idle.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/idle.c b/arch/arm64/kernel/idle.c
index c1125753fe9b..05cfb347ec26 100644
--- a/arch/arm64/kernel/idle.c
+++ b/arch/arm64/kernel/idle.c
@@ -20,7 +20,7 @@
  *	ensure that interrupts are not masked at the PMR (because the core will
  *	not wake up if we block the wake up signal in the interrupt controller).
  */
-void noinstr cpu_do_idle(void)
+void __cpuidle cpu_do_idle(void)
 {
 	struct arm_cpuidle_irq_context context;
 
@@ -35,7 +35,7 @@ void noinstr cpu_do_idle(void)
 /*
  * This is our default idle handler.
  */
-void noinstr arch_cpu_idle(void)
+void __cpuidle arch_cpu_idle(void)
 {
 	/*
 	 * This should do all the clock switching and wait for interrupt
-- 
2.42.0.283.g2d96d420d3-goog