Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit d7c53c9e authored by Borislav Petkov's avatar Borislav Petkov Committed by H. Peter Anvin
Browse files

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: default avatarBorislav Petkov <borislav.petkov@amd.com>
LKML-Reference: <20100819181029.GC17171@aftab>
Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent 8848a910

arch/x86/Kconfig

+5 −0
Original line number Original line Diff line number Diff line
@@ -245,6 +245,11 @@ config ARCH_HWEIGHT_CFLAGS 




config KTIME_SCALAR

config KTIME_SCALAR

	def_bool X86_32

	def_bool X86_32



config ARCH_CPU_PROBE_RELEASE

	def_bool y

	depends on HOTPLUG_CPU



source "init/Kconfig"

source "init/Kconfig"

source "kernel/Kconfig.freezer"

source "kernel/Kconfig.freezer"

arch/x86/kernel/smpboot.c

+19 −0
Original line number Original line 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);

static DEFINE_PER_CPU(struct task_struct *, idle_thread_array);

#define get_idle_for_cpu(x)      (per_cpu(idle_thread_array, x))

#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))

#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

#else

static struct task_struct *idle_thread_array[NR_CPUS] __cpuinitdata ;

static struct task_struct *idle_thread_array[NR_CPUS] __cpuinitdata ;

#define get_idle_for_cpu(x)      (idle_thread_array[(x)])

#define get_idle_for_cpu(x)      (idle_thread_array[(x)])