Here's the patch. It's probably more of an overkill wrt buffer heads, but
it seems to be the easiest solution.
I also put back some of the changes you made for the
bit_spin_locks, so that they act the same as the vanilla kernel if
PREEMPT_RT is not defined. Now I only tested this with PREEMPT_RT
configured so I hope others can test it with it off. If I get time I'll do
that as well.
I patched this against linux-2.6.11-rc4-V0.7.39-02, so I hope it goes
easily into .40.
Lee,
Could you see what the latencies are with kjournal with this patch
applied.
Thanks,
-- Steve
diff -ur linux-2.6.11-rc4-V0.7.39-02.orig/fs/buffer.c
linux-2.6.11-rc4-V0.7.39-02/fs/buffer.c
--- linux-2.6.11-rc4-V0.7.39-02.orig/fs/buffer.c 2005-02-12
22:06:54.000000000 -0500
+++ linux-2.6.11-rc4-V0.7.39-02/fs/buffer.c 2005-03-11 07:48:04.000000000
-0500
@@ -3002,6 +3002,10 @@
preempt_disable();
__get_cpu_var(bh_accounting).nr++;
recalc_bh_state();
+#ifdef CONFIG_PREEMPT_RT
+ spin_lock_init(&ret->b_jstate_lock);
+ spin_lock_init(&ret->b_jhead_lock);
+#endif
preempt_enable();
}
return ret;
diff -ur linux-2.6.11-rc4-V0.7.39-02.orig/include/linux/buffer_head.h
linux-2.6.11-rc4-V0.7.39-02/include/linux/buffer_head.h
--- linux-2.6.11-rc4-V0.7.39-02.orig/include/linux/buffer_head.h
2005-02-12 22:05:10.000000000 -0500
+++ linux-2.6.11-rc4-V0.7.39-02/include/linux/buffer_head.h 2005-03-11
07:59:44.000000000 -0500
@@ -62,6 +62,14 @@
bh_end_io_t *b_end_io; /* I/O completion */
void *b_private; /* reserved for b_end_io */
struct list_head b_assoc_buffers; /* associated with another mapping */
+
+#ifdef CONFIG_PREEMPT_RT
+ /*
+ * Fixme: This should be in the journal code.
+ */
+ spinlock_t b_jstate_lock; /* lock for journal state. */
+ spinlock_t b_jhead_lock; /* lock for journal head. */
+#endif
};
/*
diff -ur linux-2.6.11-rc4-V0.7.39-02.orig/include/linux/jbd.h
linux-2.6.11-rc4-V0.7.39-02/include/linux/jbd.h
--- linux-2.6.11-rc4-V0.7.39-02.orig/include/linux/jbd.h 2005-02-12
22:07:18.000000000 -0500
+++ linux-2.6.11-rc4-V0.7.39-02/include/linux/jbd.h 2005-03-11
07:57:47.000000000 -0500
@@ -314,6 +314,12 @@
TAS_BUFFER_FNS(RevokeValid, revokevalid)
BUFFER_FNS(Freed, freed)
+#ifdef CONFIG_PREEMPT_RT
+#define PICK_SPIN_LOCK(otype,bit,name) spin_##otype(&bh->b_##name##_lock)
+#else
+#define PICK_SPIN_LOCK(otype,bit,name) bit_spin_##otype(bit,bh->b_state);
+#endif
+
static inline struct buffer_head *jh2bh(struct journal_head *jh)
{
return jh->b_bh;
@@ -326,33 +332,34 @@
static inline void jbd_lock_bh_state(struct buffer_head *bh)
{
- bit_spin_lock(BH_State, &bh->b_state);
+ PICK_SPIN_LOCK(lock,BH_State,jstate);
}
static inline int jbd_trylock_bh_state(struct buffer_head *bh)
{
- return bit_spin_trylock(BH_State, &bh->b_state);
+ return PICK_SPIN_LOCK(trylock,BH_State,jstate);
}
static inline int jbd_is_locked_bh_state(struct buffer_head *bh)
{
- return bit_spin_is_locked(BH_State, &bh->b_state);
+ return PICK_SPIN_LOCK(is_locked,BH_State,jstate);
}
static inline void jbd_unlock_bh_state(struct buffer_head *bh)
{
- bit_spin_unlock(BH_State, &bh->b_state);
+ PICK_SPIN_LOCK(unlock,BH_State,jstate);
}
static inline void jbd_lock_bh_journal_head(struct buffer_head *bh)
{
- bit_spin_lock(BH_JournalHead, &bh->b_state);
+ PICK_SPIN_LOCK(lock,BH_JournalHead,jhead);
}
static inline void jbd_unlock_bh_journal_head(struct buffer_head *bh)
{
- bit_spin_unlock(BH_JournalHead, &bh->b_state);
+ PICK_SPIN_LOCK(unlock,BH_JournalHead,jhead);
}
+#undef PICK_SPIN_LOCK
struct jbd_revoke_table_s;
diff -ur linux-2.6.11-rc4-V0.7.39-02.orig/include/linux/spinlock.h
linux-2.6.11-rc4-V0.7.39-02/include/linux/spinlock.h
--- linux-2.6.11-rc4-V0.7.39-02.orig/include/linux/spinlock.h 2005-03-10
08:47:25.000000000 -0500
+++ linux-2.6.11-rc4-V0.7.39-02/include/linux/spinlock.h 2005-03-11
09:06:26.254317378 -0500
@@ -774,6 +774,10 @@
}))
+#ifndef CONFIG_PREEMPT_RT
+
+/* These are just plain evil! */
+
/*
* bit-based spin_lock()
*
@@ -789,10 +793,15 @@
* busywait with less bus contention for a good time to
* attempt to acquire the lock bit.
*/
-#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) ||
defined(CONFIG_PREEMPT)
- while (test_and_set_bit(bitnum, addr))
- while (test_bit(bitnum, addr))
+ preempt_disable();
+#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
+ while (test_and_set_bit(bitnum, addr)) {
+ while (test_bit(bitnum, addr)) {
+ preempt_enable();
cpu_relax();
+ preempt_disable();
+ }
+ }
#endif
__acquire(bitlock);
}
@@ -802,9 +811,12 @@
*/
static inline int bit_spin_trylock(int bitnum, unsigned long *addr)
{
-#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) ||
defined(CONFIG_PREEMPT)
- if (test_and_set_bit(bitnum, addr))
+ preempt_disable();
+#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
+ if (test_and_set_bit(bitnum, addr)) {
+ preempt_enable();
return 0;
+ }
#endif
__acquire(bitlock);
return 1;
@@ -815,11 +827,12 @@
*/
static inline void bit_spin_unlock(int bitnum, unsigned long *addr)
{
-#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) ||
defined(CONFIG_PREEMPT)
+#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
BUG_ON(!test_bit(bitnum, addr));
smp_mb__before_clear_bit();
clear_bit(bitnum, addr);
#endif
+ preempt_enable();
__release(bitlock);
}
@@ -828,12 +841,15 @@
*/
static inline int bit_spin_is_locked(int bitnum, unsigned long *addr)
{
-#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) ||
defined(CONFIG_PREEMPT)
+#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
return test_bit(bitnum, addr);
+#elif defined CONFIG_PREEMPT
+ return preempt_count();
#else
return 1;
#endif
}
+#endif /* CONFIG_PREEMPT_RT */
#define DEFINE_SPINLOCK(name) \
spinlock_t name __cacheline_aligned_in_smp = _SPIN_LOCK_UNLOCKED(name)
-
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