From: Robin Holt <holt@xxxxxxx>
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@xxxxxxx>
Signed-off-by: Robin Holt <holt@xxxxxxx>
Cc: <linux-arch@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: "Luck, Tony" <tony.luck@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/lockdep.h | 17 +++++++++++++++++
kernel/spinlock.c | 12 ++----------
2 files changed, 19 insertions(+), 10 deletions(-)
diff -puN include/linux/lockdep.h~factor-out-ifdefs-from-kernel-spinlockc-to-lock_contended_flags include/linux/lockdep.h
--- a/include/linux/lockdep.h~factor-out-ifdefs-from-kernel-spinlockc-to-lock_contended_flags
+++ a/include/linux/lockdep.h
@@ -364,6 +364,23 @@ do { \
#endif /* CONFIG_LOCK_STAT */
+#ifdef CONFIG_LOCKDEP
+
+/*
+ * 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 */
+
#ifdef CONFIG_GENERIC_HARDIRQS
extern void early_init_irq_lock_class(void);
#else
diff -puN kernel/spinlock.c~factor-out-ifdefs-from-kernel-spinlockc-to-lock_contended_flags kernel/spinlock.c
--- a/kernel/spinlock.c~factor-out-ifdefs-from-kernel-spinlockc-to-lock_contended_flags
+++ a/kernel/spinlock.c
@@ -299,16 +299,8 @@ unsigned long __lockfunc _spin_lock_irqs
local_irq_save(flags);
preempt_disable();
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:
- */
-#ifdef CONFIG_LOCKDEP
- LOCK_CONTENDED(lock, _raw_spin_trylock, _raw_spin_lock);
-#else
- _raw_spin_lock_flags(lock, &flags);
-#endif
+ LOCK_CONTENDED_FLAGS(lock, _raw_spin_trylock, _raw_spin_lock,
+ _raw_spin_lock_flags, &flags);
return flags;
}
EXPORT_SYMBOL(_spin_lock_irqsave_nested);
_
--
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