Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 fixes from Catalin Marinas:

 - smp_mb__before_spinlock() changed to smp_mb() on arm64 since the
   generic definition to smp_wmb() is not sufficient

 - avoid a recursive loop with the graph tracer by using using
   preempt_(enable|disable)_notrace in _percpu_(read|write)

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: use preempt_disable_notrace in _percpu_read/write
  arm64: spinlocks: implement smp_mb__before_spinlock() as smp_mb()

diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h
index 0a456be..2fee2f5 100644 (file)
--- a/arch/arm64/include/asm/percpu.h
+++ b/arch/arm64/include/asm/percpu.h
@@ -199,19 +199,19 @@ static inline unsigned long __percpu_xchg(void *ptr, unsigned long val,
 #define _percpu_read(pcp)                                              \
 ({                                                                     \
        typeof(pcp) __retval;                                           \
-       preempt_disable();                                              \
+       preempt_disable_notrace();                                      \
        __retval = (typeof(pcp))__percpu_read(raw_cpu_ptr(&(pcp)),      \
                                              sizeof(pcp));             \
-       preempt_enable();                                               \
+       preempt_enable_notrace();                                       \
        __retval;                                                       \
 })
 
 #define _percpu_write(pcp, val)                                                \
 do {                                                                   \
-       preempt_disable();                                              \
+       preempt_disable_notrace();                                      \
        __percpu_write(raw_cpu_ptr(&(pcp)), (unsigned long)(val),       \
                                sizeof(pcp));                           \
-       preempt_enable();                                               \
+       preempt_enable_notrace();                                       \
 } while(0)                                                             \
 
 #define _pcp_protect(operation, pcp, val)                      \

diff --git a/arch/arm64/include/asm/spinlock.h b/arch/arm64/include/asm/spinlock.h
index e875a5a..89206b5 100644 (file)
--- a/arch/arm64/include/asm/spinlock.h
+++ b/arch/arm64/include/asm/spinlock.h
@@ -363,4 +363,14 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
 #define arch_read_relax(lock)  cpu_relax()
 #define arch_write_relax(lock) cpu_relax()
 
+/*
+ * Accesses appearing in program order before a spin_lock() operation
+ * can be reordered with accesses inside the critical section, by virtue
+ * of arch_spin_lock being constructed using acquire semantics.
+ *
+ * In cases where this is problematic (e.g. try_to_wake_up), an
+ * smp_mb__before_spinlock() can restore the required ordering.
+ */
+#define smp_mb__before_spinlock()      smp_mb()
+
 #endif /* __ASM_SPINLOCK_H */