* Arjan van de Ven <[email protected]> wrote:
> > Is that intentional though? With <randon .config> my mm/swapfile.i has an
> > unreferenced
> >
> > static inline void __raw_spin_unlock(raw_spinlock_t *lock)
> > {
> > __asm__ __volatile__(
> > "movb $1,%0" :"=m" (lock->slock) : : "memory"
> > );
> > }
> >
> > which either a) shouldn't be there or b) should be referenced.
> >
> > Ingo, can you confirm that x86's spin_unlock is never inlined? If so,
> > what's my __raw_spin_unlock() doing there?
__raw_spin_unlock is currently only inlined in the kernel/spinlock.c
code.
> I would really want this one inlined! A movb is a much shorter code
> sequence than a call (esp if you factor in argument setup).
> De-inlining to save space is nice and all, but it can go too far....
yeah, it makes sense to inline the single-instruction unlock operations:
nondebug spin_unlock(), read_unlock() and write_unlock(). This gives a
0.2% code-size reduction:
text data bss dec hex filename
4072031 858208 387196 5317435 51233b vmlinux-smp-uninlined
4060671 858212 387196 5306079 50f6df vmlinux-smp-inlined
patch against -rc5. Boot-tested on a 4-way x86 SMP box.
Ingo
Signed-off-by: Ingo Molnar <[email protected]>
include/linux/spinlock.h | 15 ++++++++++++---
1 files changed, 12 insertions(+), 3 deletions(-)
Index: linux/include/linux/spinlock.h
===================================================================
--- linux.orig/include/linux/spinlock.h
+++ linux/include/linux/spinlock.h
@@ -171,9 +171,18 @@ extern int __lockfunc generic__raw_read_
#define write_lock_irq(lock) _write_lock_irq(lock)
#define write_lock_bh(lock) _write_lock_bh(lock)
-#define spin_unlock(lock) _spin_unlock(lock)
-#define write_unlock(lock) _write_unlock(lock)
-#define read_unlock(lock) _read_unlock(lock)
+/*
+ * We inline the unlock functions in the nondebug case:
+ */
+#ifdef CONFIG_DEBUG_SPINLOCK
+# define spin_unlock(lock) _spin_unlock(lock)
+# define read_unlock(lock) _read_unlock(lock)
+# define write_unlock(lock) _write_unlock(lock)
+#else
+# define spin_unlock(lock) __raw_spin_unlock(&(lock)->raw_lock)
+# define read_unlock(lock) __raw_read_unlock(&(lock)->raw_lock)
+# define write_unlock(lock) __raw_write_unlock(&(lock)->raw_lock)
+#endif
#define spin_unlock_irqrestore(lock, flags) \
_spin_unlock_irqrestore(lock, flags)
-
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