Factor out #ifdefs from kernel/spinlock.c to LOCK_CONTENDED_FLAGS
Robin Holt [Thu, 2 Apr 2009 23:59:45 +0000 (16:59 -0700)]
SGI has observed that on large systems, interrupts are not serviced for a
long period of time when waiting for a rwlock.  The following patch series
re-enables irqs while waiting for the lock, resembling the code which is
already there for spinlocks.

I only made the ia64 version, because the patch adds some overhead to the
fast path.  I assume there is currently no demand to have this for other
architectures, because the systems are not so large.  Of course, the
possibility to implement raw_{read|write}_lock_flags for any architecture
is still there.

This patch:

The new macro LOCK_CONTENDED_FLAGS expands to the correct implementation
depending on the config options, so that IRQ's are re-enabled when
possible, but they remain disabled if CONFIG_LOCKDEP is set.

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
Signed-off-by: Robin Holt <holt@sgi.com>
Cc: <linux-arch@vger.kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


index 5a58ea3..da5a5a1 100644 (file)
@@ -364,6 +364,23 @@ do {                                                               \
 #endif /* CONFIG_LOCK_STAT */
+ * On lockdep we dont want the hand-coded irq-enable of
+ * _raw_*_lock_flags() code, because lockdep assumes
+ * that interrupts are not re-enabled during lock-acquire:
+ */
+#define LOCK_CONTENDED_FLAGS(_lock, try, lock, lockfl, flags) \
+       LOCK_CONTENDED((_lock), (try), (lock))
+#else /* CONFIG_LOCKDEP */
+#define LOCK_CONTENDED_FLAGS(_lock, try, lock, lockfl, flags) \
+       lockfl((_lock), (flags))
+#endif /* CONFIG_LOCKDEP */
 extern void early_init_irq_lock_class(void);
index 29ab207..7283c6d 100644 (file)
@@ -299,16 +299,8 @@ unsigned long __lockfunc _spin_lock_irqsave_nested(spinlock_t *lock, int subclas
        spin_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
-       /*
-        * On lockdep we dont want the hand-coded irq-enable of
-        * _raw_spin_lock_flags() code, because lockdep assumes
-        * that interrupts are not re-enabled during lock-acquire:
-        */
-       LOCK_CONTENDED(lock, _raw_spin_trylock, _raw_spin_lock);
-       _raw_spin_lock_flags(lock, &flags);
+       LOCK_CONTENDED_FLAGS(lock, _raw_spin_trylock, _raw_spin_lock,
+                               _raw_spin_lock_flags, &flags);
        return flags;