[PATCH v7 4/4] nmi_backtrace: generate one-line reports for idle cpus
From: mark.rutland@arm.com (Mark Rutland)
Date: 2016-08-08 16:48:44
Also in:
linux-arch, lkml
Hi, [adding Lorenzo] On Mon, Aug 08, 2016 at 12:03:38PM -0400, Chris Metcalf wrote:
When doing an nmi backtrace of many cores, most of which are idle, the output is a little overwhelming and very uninformative. Suppress messages for cpus that are idling when they are interrupted and just emit one line, "NMI backtrace for N skipped: idling at pc 0xNNN". We do this by grouping all the cpuidle code together into a new .cpuidle.text section, and then checking the address of the interrupted PC to see if it lies within that section. This commit suitably tags x86, arm64, and tile idle routines, and only adds in the minimal framework for other architectures.
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 659963d40bb4..fe7f93b7b11b 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S@@ -122,6 +122,7 @@ SECTIONS ENTRY_TEXT TEXT_TEXT SCHED_TEXT + CPUIDLE_TEXT LOCK_TEXT KPROBES_TEXT HYPERVISOR_TEXTdiff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index 5bb61de23201..64f088ca3192 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S@@ -48,11 +48,13 @@ * * Idle the processor (wait for interrupt). */ + .pushsection ".cpuidle.text","ax" ENTRY(cpu_do_idle) dsb sy // WFI may enter a low-power mode wfi ret ENDPROC(cpu_do_idle) + .popsection
From a quick scan it looks like we only call this with interrupts
disabled, and we have no NMI. So shouldn't we be annotating arch_cpu_idle(), which calls this and subsequently enables interrupts? I'm also not sure what you need to do for PSCI, which is the preferred (FW-backed) idle mechanism for arm64. The infrastrucure for that is spread over a few files: arch/arm64/kernel/sleep.S arch/arm64/kernel/smccc-call.S arch/arm64/kernel/suspend.c drivers/cpuidle/cpuidle-arm.c drivers/firmware/psci.c I'm not sure where we'd be an an interruptible state, and therefore I'm not immediately sure what we should annotate. Thanks, Mark.