linux-kernel - [PATCH 2/2] arm64: smp: Don't directly call arch_smp_send

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Date:   Mon,  2 Oct 2023 09:45:30 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Marc Zyngier <maz@...nel.org>
Cc:     Stephen Boyd <swboyd@...omium.org>,
        Valentin Schneider <vschneid@...hat.com>,
        Chen-Yu Tsai <wenst@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        D Scott Phillips <scott@...amperecomputing.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Sumit Garg <sumit.garg@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] arm64: smp: Don't directly call arch_smp_send_reschedule() for wakeup

In commit 2b2d0a7a96ab ("arm64: smp: Remove dedicated wakeup IPI") we
started using a scheduler IPI to avoid a dedicated reschedule. When we
did this, we used arch_smp_send_reschedule() directly rather than
calling smp_send_reschedule(). The only difference is that calling
arch_smp_send_reschedule() directly avoids tracing. Presumably we
_don't_ want to avoid tracing here, so switch to
smp_send_reschedule().

Fixes: 2b2d0a7a96ab ("arm64: smp: Remove dedicated wakeup IPI")
Signed-off-by: Douglas Anderson <dianders@...omium.org>
---
I don't 100% know if this is correct and I don't have any hardware
that uses the "ACPI parking protocol", but I think it's right. My main
incentive for this is that it makes it easier to backport pseudo-NMI
to kernels that don't have arch_smp_send_reschedule(), but I think
it's also more correct.

If for some reason we truly did want to avoid tracing here, please
shout and we can drop this patch.

 arch/arm64/kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 0a6002243a8c..b530d8ef9c1d 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -1063,7 +1063,7 @@ void arch_send_wakeup_ipi(unsigned int cpu)
 	 * We use a scheduler IPI to wake the CPU as this avoids the need for a
 	 * dedicated IPI and we can safely handle spurious scheduler IPIs.
 	 */
-	arch_smp_send_reschedule(cpu);
+	smp_send_reschedule(cpu);
 }
 #endif
 
-- 
2.42.0.582.g8ccd20d70d-goog