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Subject[PATCH 2/2] debug_core: replace atomic_set() with atomic_xchg() for atomic kgdb_active
Date
The atomic_set() don't imply memory barriers, therefor the single
stepping processor could not observe the changing of kgdb_active
value which was done at other cpu immediately.

Using atomic_xchg() to replace atomic_set() to change kgdb_active,
as it implys the memory barrier semantics around the atomic_xchg().

Signed-off-by: Dongdong Deng <libfetion@gmail.com>
---
kernel/debug/debug_core.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index bec8af0..722968f 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -548,7 +548,7 @@ return_normal:
if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
(kgdb_info[cpu].task &&
kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
- atomic_set(&kgdb_active, -1);
+ atomic_xchg(&kgdb_active, -1);
raw_spin_unlock(&dbg_master_lock);
dbg_touch_watchdogs();
local_irq_restore(flags);
@@ -657,7 +657,7 @@ kgdb_restore:
smp_mb__before_atomic_dec();
atomic_dec(&masters_in_kgdb);
/* Free kgdb_active */
- atomic_set(&kgdb_active, -1);
+ atomic_xchg(&kgdb_active, -1);
raw_spin_unlock(&dbg_master_lock);
dbg_touch_watchdogs();
local_irq_restore(flags);
--
1.6.0.4


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