s390/preempt: move preempt_count to the lowcore
Convert s390 to use a field in the struct lowcore for the CPU
preemption count. It is a bit cheaper to access a lowcore field
compared to a thread_info variable and it removes the depencency
on a task related structure.
bloat-o-meter on the vmlinux image for the default configuration
(CONFIG_PREEMPT_NONE=y) reports a small reduction in text size:
add/remove: 0/0 grow/shrink: 18/578 up/down: 228/-5448 (-5220)
A larger improvement is achieved with the default configuration
but with CONFIG_PREEMPT=y and CONFIG_DEBUG_PREEMPT=n:
add/remove: 2/6 grow/shrink: 59/4477 up/down: 1618/-228762 (-227144)
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/preempt.h b/arch/s390/include/asm/preempt.h
new file mode 100644
index 0000000..b0776b2
--- /dev/null
+++ b/arch/s390/include/asm/preempt.h
@@ -0,0 +1,137 @@
+#ifndef __ASM_PREEMPT_H
+#define __ASM_PREEMPT_H
+
+#include <asm/current.h>
+#include <linux/thread_info.h>
+#include <asm/atomic_ops.h>
+
+#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
+
+#define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED)
+
+static inline int preempt_count(void)
+{
+ return READ_ONCE(S390_lowcore.preempt_count) & ~PREEMPT_NEED_RESCHED;
+}
+
+static inline void preempt_count_set(int pc)
+{
+ int old, new;
+
+ do {
+ old = READ_ONCE(S390_lowcore.preempt_count);
+ new = (old & PREEMPT_NEED_RESCHED) |
+ (pc & ~PREEMPT_NEED_RESCHED);
+ } while (__atomic_cmpxchg(&S390_lowcore.preempt_count,
+ old, new) != old);
+}
+
+#define init_task_preempt_count(p) do { } while (0)
+
+#define init_idle_preempt_count(p, cpu) do { \
+ S390_lowcore.preempt_count = PREEMPT_ENABLED; \
+} while (0)
+
+static inline void set_preempt_need_resched(void)
+{
+ __atomic_and(~PREEMPT_NEED_RESCHED, &S390_lowcore.preempt_count);
+}
+
+static inline void clear_preempt_need_resched(void)
+{
+ __atomic_or(PREEMPT_NEED_RESCHED, &S390_lowcore.preempt_count);
+}
+
+static inline bool test_preempt_need_resched(void)
+{
+ return !(READ_ONCE(S390_lowcore.preempt_count) & PREEMPT_NEED_RESCHED);
+}
+
+static inline void __preempt_count_add(int val)
+{
+ if (__builtin_constant_p(val) && (val >= -128) && (val <= 127))
+ __atomic_add_const(val, &S390_lowcore.preempt_count);
+ else
+ __atomic_add(val, &S390_lowcore.preempt_count);
+}
+
+static inline void __preempt_count_sub(int val)
+{
+ __preempt_count_add(-val);
+}
+
+static inline bool __preempt_count_dec_and_test(void)
+{
+ return __atomic_add(-1, &S390_lowcore.preempt_count) == 1;
+}
+
+static inline bool should_resched(int preempt_offset)
+{
+ return unlikely(READ_ONCE(S390_lowcore.preempt_count) ==
+ preempt_offset);
+}
+
+#else /* CONFIG_HAVE_MARCH_Z196_FEATURES */
+
+#define PREEMPT_ENABLED (0)
+
+static inline int preempt_count(void)
+{
+ return READ_ONCE(S390_lowcore.preempt_count);
+}
+
+static inline void preempt_count_set(int pc)
+{
+ S390_lowcore.preempt_count = pc;
+}
+
+#define init_task_preempt_count(p) do { } while (0)
+
+#define init_idle_preempt_count(p, cpu) do { \
+ S390_lowcore.preempt_count = PREEMPT_ENABLED; \
+} while (0)
+
+static inline void set_preempt_need_resched(void)
+{
+}
+
+static inline void clear_preempt_need_resched(void)
+{
+}
+
+static inline bool test_preempt_need_resched(void)
+{
+ return false;
+}
+
+static inline void __preempt_count_add(int val)
+{
+ S390_lowcore.preempt_count += val;
+}
+
+static inline void __preempt_count_sub(int val)
+{
+ S390_lowcore.preempt_count -= val;
+}
+
+static inline bool __preempt_count_dec_and_test(void)
+{
+ return !--S390_lowcore.preempt_count && tif_need_resched();
+}
+
+static inline bool should_resched(int preempt_offset)
+{
+ return unlikely(preempt_count() == preempt_offset &&
+ tif_need_resched());
+}
+
+#endif /* CONFIG_HAVE_MARCH_Z196_FEATURES */
+
+#ifdef CONFIG_PREEMPT
+extern asmlinkage void preempt_schedule(void);
+#define __preempt_schedule() preempt_schedule()
+extern asmlinkage void preempt_schedule_notrace(void);
+#define __preempt_schedule_notrace() preempt_schedule_notrace()
+#endif /* CONFIG_PREEMPT */
+
+#endif /* __ASM_PREEMPT_H */