From c814ca029e1015bb0ecec312f4bb9751ba1a711a Mon Sep 17 00:00:00 2001 From: Ashwin Chaugule Date: Wed, 7 May 2014 10:18:36 -0400 Subject: ARM: Check if a CPU has gone offline PSCIv0.2 adds a new function called AFFINITY_INFO, which can be used to query if a specified CPU has actually gone offline. Calling this function via cpu_kill ensures that a CPU has quiesced after a call to cpu_die. This helps prevent the CPU from doing arbitrary bad things when data or instructions are clobbered (as happens with kexec) in the window between a CPU announcing that it is dead and said CPU leaving the kernel. Signed-off-by: Ashwin Chaugule Signed-off-by: Mark Rutland Reviewed-by: Rob Herring Acked-by: Catalin Marinas --- arch/arm/kernel/psci_smp.c | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) (limited to 'arch/arm/kernel/psci_smp.c') diff --git a/arch/arm/kernel/psci_smp.c b/arch/arm/kernel/psci_smp.c index 570a48cc3d64..28a1db4da704 100644 --- a/arch/arm/kernel/psci_smp.c +++ b/arch/arm/kernel/psci_smp.c @@ -16,6 +16,8 @@ #include #include #include +#include +#include #include #include @@ -66,6 +68,36 @@ void __ref psci_cpu_die(unsigned int cpu) /* We should never return */ panic("psci: cpu %d failed to shutdown\n", cpu); } + +int __ref psci_cpu_kill(unsigned int cpu) +{ + int err, i; + + if (!psci_ops.affinity_info) + return 1; + /* + * cpu_kill could race with cpu_die and we can + * potentially end up declaring this cpu undead + * while it is dying. So, try again a few times. + */ + + for (i = 0; i < 10; i++) { + err = psci_ops.affinity_info(cpu_logical_map(cpu), 0); + if (err == PSCI_0_2_AFFINITY_LEVEL_OFF) { + pr_info("CPU%d killed.\n", cpu); + return 1; + } + + msleep(10); + pr_info("Retrying again to check for CPU kill\n"); + } + + pr_warn("CPU%d may not have shut down cleanly (AFFINITY_INFO reports %d)\n", + cpu, err); + /* Make platform_cpu_kill() fail. */ + return 0; +} + #endif bool __init psci_smp_available(void) @@ -78,5 +110,6 @@ struct smp_operations __initdata psci_smp_ops = { .smp_boot_secondary = psci_boot_secondary, #ifdef CONFIG_HOTPLUG_CPU .cpu_die = psci_cpu_die, + .cpu_kill = psci_cpu_kill, #endif }; -- cgit v1.2.3