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x86, hotplug: Serialize CPU hotplug to avoid bringup concurrency issues

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>
master
Borislav Petkov 11 years ago
committed by H. Peter Anvin
parent
commit
d7c53c9e82
  1. 5
      arch/x86/Kconfig
  2. 19
      arch/x86/kernel/smpboot.c

5
arch/x86/Kconfig

@ -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"

19
arch/x86/kernel/smpboot.c

@ -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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