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Commit 8c5a1cf0 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
Browse files

kexec: use a mutex for locking rather than xchg() 



Functionally the same, but more conventional.

Cc: Huang Ying <ying.huang@intel.com>
Tested-by: default avatarVivek Goyal <vgoyal@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3122c331

kernel/kexec.c

+10 −24
Original line number Diff line number Diff line
@@ -12,7 +12,7 @@ 
#include <linux/slab.h>

#include <linux/fs.h>

#include <linux/kexec.h>

#include <linux/spinlock.h>

#include <linux/mutex.h>

#include <linux/list.h>

#include <linux/highmem.h>

#include <linux/syscalls.h>
@@ -924,19 +924,14 @@ static int kimage_load_segment(struct kimage *image, 
 */

struct kimage *kexec_image;

struct kimage *kexec_crash_image;

/*

 * A home grown binary mutex.

 * Nothing can wait so this mutex is safe to use

 * in interrupt context :)

 */

static int kexec_lock;



static DEFINE_MUTEX(kexec_mutex);



asmlinkage long sys_kexec_load(unsigned long entry, unsigned long nr_segments,

				struct kexec_segment __user *segments,

				unsigned long flags)

{

	struct kimage **dest_image, *image;

	int locked;

	int result;



	/* We only trust the superuser with rebooting the system. */
@@ -972,8 +967,7 @@ asmlinkage long sys_kexec_load(unsigned long entry, unsigned long nr_segments, 
	 *

	 * KISS: always take the mutex.

	 */

	locked = xchg(&kexec_lock, 1);

	if (locked)

	if (!mutex_trylock(&kexec_mutex))

		return -EBUSY;



	dest_image = &kexec_image;
@@ -1015,8 +1009,7 @@ asmlinkage long sys_kexec_load(unsigned long entry, unsigned long nr_segments, 
	image = xchg(dest_image, image);



out:

	locked = xchg(&kexec_lock, 0); /* Release the mutex */

	BUG_ON(!locked);

	mutex_unlock(&kexec_mutex);

	kimage_free(image);



	return result;
@@ -1063,10 +1056,7 @@ asmlinkage long compat_sys_kexec_load(unsigned long entry, 


void crash_kexec(struct pt_regs *regs)

{

	int locked;





	/* Take the kexec_lock here to prevent sys_kexec_load

	/* Take the kexec_mutex here to prevent sys_kexec_load

	 * running on one cpu from replacing the crash kernel

	 * we are using after a panic on a different cpu.

	 *
@@ -1074,8 +1064,7 @@ void crash_kexec(struct pt_regs *regs) 
	 * of memory the xchg(&kexec_crash_image) would be

	 * sufficient.  But since I reuse the memory...

	 */

	locked = xchg(&kexec_lock, 1);

	if (!locked) {

	if (mutex_trylock(&kexec_mutex)) {

		if (kexec_crash_image) {

			struct pt_regs fixed_regs;

			crash_setup_regs(&fixed_regs, regs);
@@ -1083,8 +1072,7 @@ void crash_kexec(struct pt_regs *regs) 
			machine_crash_shutdown(&fixed_regs);

			machine_kexec(kexec_crash_image);

		}

		locked = xchg(&kexec_lock, 0);

		BUG_ON(!locked);

		mutex_unlock(&kexec_mutex);

	}

}
@@ -1434,7 +1422,7 @@ int kernel_kexec(void) 
{

	int error = 0;



	if (xchg(&kexec_lock, 1))

	if (!mutex_trylock(&kexec_mutex))

		return -EBUSY;

	if (!kexec_image) {

		error = -EINVAL;
@@ -1498,8 +1486,6 @@ int kernel_kexec(void) 
#endif



 Unlock:

	if (!xchg(&kexec_lock, 0))

		BUG();



	mutex_unlock(&kexec_mutex);

	return error;

}