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: Will Deacon <will.deacon@arm.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

1 files changed, 7 insertions, 8 deletions

diff --git a/kernel/kgdb.c b/kernel/kgdb.c
index 6882c047452d..2f7f454605c2 100644
--- a/kernel/kgdb.c
+++ b/kernel/kgdb.c
@@ -1379,8 +1379,7 @@ acquirelock:
          * 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 @@ return_normal:
                          */
                         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 @@ return_normal:
          */
         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 @@ return_normal:
         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);