x86, hotplug: Serialize CPU hotplug to avoid bringup concurrency issues (d7c53c9e) · Commits · 戴 / test

When testing cpu hotplug code on 32-bit we kept hitting the "CPU%d: Stuck ??" message due to multiple cores concurrently accessing the cpu_callin_mask, among others. Since these codepaths are not protected from concurrent access due to the fact that there's no sane reason for making an already complex code unnecessarily more complex - we hit the issue only when insanely switching cores off- and online - serialize hotplugging cores on the sysfs level and be done with it. [ v2.1: fix !HOTPLUG_CPU build ] Cc: <stable@kernel.org> Signed-off-by:

Borislav Petkov <borislav.petkov@amd.com> LKML-Reference: <20100819181029.GC17171@aftab> Signed-off-by:

H. Peter Anvin <hpa@linux.intel.com>

arch/x86/Kconfig

+5 −0

Original line number	Diff line number	Diff line
		@@ -245,6 +245,11 @@ config ARCH_HWEIGHT_CFLAGS

		config KTIME_SCALAR
		def_bool X86_32

		config ARCH_CPU_PROBE_RELEASE
		def_bool y
		depends on HOTPLUG_CPU

		source "init/Kconfig"
		source "kernel/Kconfig.freezer"

arch/x86/kernel/smpboot.c

+19 −0

Original line number	Diff line number	Diff line
		@@ -90,6 +90,25 @@ DEFINE_PER_CPU(int, cpu_state) = { 0 };
		static DEFINE_PER_CPU(struct task_struct *, idle_thread_array);
		#define get_idle_for_cpu(x) (per_cpu(idle_thread_array, x))
		#define set_idle_for_cpu(x, p) (per_cpu(idle_thread_array, x) = (p))

		/*
		* We need this for trampoline_base protection from concurrent accesses when
		* off- and onlining cores wildly.
		*/
		static DEFINE_MUTEX(x86_cpu_hotplug_driver_mutex);

		void cpu_hotplug_driver_lock()
		{
		mutex_lock(&x86_cpu_hotplug_driver_mutex);
		}

		void cpu_hotplug_driver_unlock()
		{
		mutex_unlock(&x86_cpu_hotplug_driver_mutex);
		}

		ssize_t arch_cpu_probe(const char *buf, size_t count) { return -1; }
		ssize_t arch_cpu_release(const char *buf, size_t count) { return -1; }
		#else
		static struct task_struct *idle_thread_array[NR_CPUS] __cpuinitdata ;
		#define get_idle_for_cpu(x) (idle_thread_array[(x)])

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