[PATCH v11 2/6] arm64: idle: Tag the arm64 idle functions as __cpuidle

From: Douglas Anderson <dianders@chromium.org>
To: Mark Rutland <mark.rutland@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Sumit Garg <sumit.garg@linaro.org>,
	Daniel Thompson <daniel.thompson@linaro.org>,
	Marc Zyngier <maz@kernel.org>
Cc: "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	kgdb-bugreport@lists.sourceforge.net,
	Lecopzer Chen <lecopzer.chen@mediatek.com>,
	linux-perf-users@vger.kernel.org,
	Masayoshi Mizuma <msys.mizuma@gmail.com>,
	Chen-Yu Tsai <wens@csie.org>,
	linux-arm-kernel@lists.infradead.org, ito-yuichi@fujitsu.com,
	Stephen Boyd <swboyd@chromium.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Douglas Anderson <dianders@chromium.org>,
	Frederic Weisbecker <frederic@kernel.org>,
	Guo Ren <guoren@kernel.org>, Ingo Molnar <mingo@kernel.org>,
	linux-kernel@vger.kernel.org
Subject: [PATCH v11 2/6] arm64: idle: Tag the arm64 idle functions as __cpuidle
Date: Thu, 24 Aug 2023 08:30:28 -0700	[thread overview]
Message-ID: <20230824083012.v11.2.I4baba13e220bdd24d11400c67f137c35f07f82c7@changeid> (raw)
In-Reply-To: <20230824153233.1006420-1-dianders@chromium.org>

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@arm.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

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.rc1.204.g551eb34607-goog

