Messages in this thread Patch in this message | | | From | Pingfan Liu <> | Subject | [RFC 10/10] arm64: smp: Make __cpu_disable() parallel | Date | Mon, 22 Aug 2022 10:15:20 +0800 |
| |
On a dying cpu, take_cpu_down()->__cpu_disable(), which means if the teardown path supports parallel, __cpu_disable() confront the parallel, which may ruin cpu_online_mask etc if no extra lock provides the protection.
At present, the cpumask is protected by cpu_add_remove_lock, that lock is quite above __cpu_disable(). In order to protect __cpu_disable() from parrallel in kexec quick reboot path, introducing a local lock cpumap_lock.
Signed-off-by: Pingfan Liu <kernelfans@gmail.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Viresh Kumar <viresh.kumar@linaro.org> Cc: Sudeep Holla <sudeep.holla@arm.com> Cc: Phil Auld <pauld@redhat.com> Cc: Rob Herring <robh@kernel.org> Cc: Ben Dooks <ben-linux@fluff.org> To: linux-arm-kernel@lists.infradead.org To: linux-kernel@vger.kernel.org --- arch/arm64/kernel/smp.c | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-)
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index ffc5d76cf695..fee8879048b0 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -287,6 +287,28 @@ static int op_cpu_disable(unsigned int cpu) return 0; } +static DEFINE_SPINLOCK(cpumap_lock); + +static void __cpu_clear_maps(unsigned int cpu) +{ + /* + * In the case of kexec rebooting, the cpu_add_remove_lock mutex can not protect + */ + if (kexec_in_progress) + spin_lock(&cpumap_lock); + remove_cpu_topology(cpu); + numa_remove_cpu(cpu); + + /* + * Take this CPU offline. Once we clear this, we can't return, + * and we must not schedule until we're ready to give up the cpu. + */ + set_cpu_online(cpu, false); + if (kexec_in_progress) + spin_unlock(&cpumap_lock); + +} + /* * __cpu_disable runs on the processor to be shutdown. */ @@ -299,14 +321,7 @@ int __cpu_disable(void) if (ret) return ret; - remove_cpu_topology(cpu); - numa_remove_cpu(cpu); - - /* - * Take this CPU offline. Once we clear this, we can't return, - * and we must not schedule until we're ready to give up the cpu. - */ - set_cpu_online(cpu, false); + __cpu_clear_maps(cpu); ipi_teardown(cpu); /* -- 2.31.1
| |