Commit ae6bf53e authored by Jason Wessel's avatar Jason Wessel
Browse files

kgdb: use atomic_inc and atomic_dec instead of atomic_set 



Memory barriers should be used for the kgdb cpu synchronization.  The
atomic_set() does not imply a memory barrier.

Reported-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarJason Wessel <jason.wessel@windriver.com>
parent 62fae312

kernel/kgdb.c

+7 −8
Original line number Diff line number Diff line
@@ -1379,8 +1379,7 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs) 
	 * Make sure the above info reaches the primary CPU before

	 * our cpu_in_kgdb[] flag setting does:

	 */

	smp_wmb();

	atomic_set(&cpu_in_kgdb[cpu], 1);

	atomic_inc(&cpu_in_kgdb[cpu]);



	/*

	 * CPU will loop if it is a slave or request to become a kgdb
@@ -1400,7 +1399,7 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs) 
			 */

			if (arch_kgdb_ops.correct_hw_break)

				arch_kgdb_ops.correct_hw_break();

			atomic_set(&cpu_in_kgdb[cpu], 0);

			atomic_dec(&cpu_in_kgdb[cpu]);

			touch_softlockup_watchdog_sync();

			clocksource_touch_watchdog();

			local_irq_restore(flags);
@@ -1449,7 +1448,7 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs) 
	 */

	if (!kgdb_single_step) {

		for (i = 0; i < NR_CPUS; i++)

			atomic_set(&passive_cpu_wait[i], 1);

			atomic_inc(&passive_cpu_wait[i]);

	}



#ifdef CONFIG_SMP
@@ -1483,11 +1482,11 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs) 
	if (kgdb_io_ops->post_exception)

		kgdb_io_ops->post_exception();



	atomic_set(&cpu_in_kgdb[ks->cpu], 0);

	atomic_dec(&cpu_in_kgdb[ks->cpu]);



	if (!kgdb_single_step) {

		for (i = NR_CPUS-1; i >= 0; i--)

			atomic_set(&passive_cpu_wait[i], 0);

			atomic_dec(&passive_cpu_wait[i]);

		/*

		 * Wait till all the CPUs have quit

		 * from the debugger.
@@ -1736,11 +1735,11 @@ EXPORT_SYMBOL_GPL(kgdb_unregister_io_module); 
 */

void kgdb_breakpoint(void)

{

	atomic_set(&kgdb_setting_breakpoint, 1);

	atomic_inc(&kgdb_setting_breakpoint);

	wmb(); /* Sync point before breakpoint */

	arch_kgdb_breakpoint();

	wmb(); /* Sync point after breakpoint */

	atomic_set(&kgdb_setting_breakpoint, 0);

	atomic_dec(&kgdb_setting_breakpoint);

}

EXPORT_SYMBOL_GPL(kgdb_breakpoint);