From: Ravikiran G Thirumalai <kiran@scalex86.org>

Add percpu_counter_mod_bh for using these counters safely from both softirq
and process context.

Signed-off-by: Pravin B. Shelar <pravins@calsoftinc.com>
Signed-off-by: Ravikiran G Thirumalai <kiran@scalex86.org>
Signed-off-by: Shai Fultheim <shai@scalex86.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 include/linux/percpu_counter.h |    9 +++++++++
 mm/swap.c                      |   23 +++++++++++++++++++----
 2 files changed, 28 insertions(+), 4 deletions(-)

diff -puN include/linux/percpu_counter.h~per-cpufy-net-proto-structures-add-percpu_counter_modbh include/linux/percpu_counter.h
--- devel/include/linux/percpu_counter.h~per-cpufy-net-proto-structures-add-percpu_counter_modbh	2006-03-16 02:08:41.000000000 -0800
+++ devel-akpm/include/linux/percpu_counter.h	2006-03-16 02:08:41.000000000 -0800
@@ -11,6 +11,7 @@
 #include <linux/smp.h>
 #include <linux/threads.h>
 #include <linux/percpu.h>
+#include <linux/interrupt.h>
 
 #ifdef CONFIG_SMP
 
@@ -40,6 +41,7 @@ static inline void percpu_counter_destro
 
 void percpu_counter_mod(struct percpu_counter *fbc, long amount);
 long percpu_counter_sum(struct percpu_counter *fbc);
+void percpu_counter_mod_bh(struct percpu_counter *fbc, long amount);
 
 static inline long percpu_counter_read(struct percpu_counter *fbc)
 {
@@ -98,6 +100,12 @@ static inline long percpu_counter_sum(st
 	return percpu_counter_read_positive(fbc);
 }
 
+static inline void percpu_counter_mod_bh(struct percpu_counter *fbc, long amount)
+{
+	local_bh_disable();
+	fbc->count += amount;
+	local_bh_enable();
+}
 #endif	/* CONFIG_SMP */
 
 static inline void percpu_counter_inc(struct percpu_counter *fbc)
@@ -110,4 +118,5 @@ static inline void percpu_counter_dec(st
 	percpu_counter_mod(fbc, -1);
 }
 
+
 #endif /* _LINUX_PERCPU_COUNTER_H */
diff -puN mm/swap.c~per-cpufy-net-proto-structures-add-percpu_counter_modbh mm/swap.c
--- devel/mm/swap.c~per-cpufy-net-proto-structures-add-percpu_counter_modbh	2006-03-16 02:08:41.000000000 -0800
+++ devel-akpm/mm/swap.c	2006-03-16 02:08:41.000000000 -0800
@@ -480,11 +480,11 @@ static int cpu_swap_callback(struct noti
 #endif /* CONFIG_SMP */
 
 #ifdef CONFIG_SMP
-void percpu_counter_mod(struct percpu_counter *fbc, long amount)
+static void __percpu_counter_mod(struct percpu_counter *fbc, long amount)
 {
 	long count;
 	long *pcount;
-	int cpu = get_cpu();
+	int cpu = smp_processor_id();
 
 	pcount = per_cpu_ptr(fbc->counters, cpu);
 	count = *pcount + amount;
@@ -496,9 +496,21 @@ void percpu_counter_mod(struct percpu_co
 	} else {
 		*pcount = count;
 	}
-	put_cpu();
 }
-EXPORT_SYMBOL(percpu_counter_mod);
+
+void percpu_counter_mod(struct percpu_counter *fbc, long amount)
+{
+	preempt_disable();
+	__percpu_counter_mod(fbc, amount);
+	preempt_enable();
+}
+
+void percpu_counter_mod_bh(struct percpu_counter *fbc, long amount)
+{
+	local_bh_disable();
+	__percpu_counter_mod(fbc, amount);
+	local_bh_enable();
+}
 
 /*
  * Add up all the per-cpu counts, return the result.  This is a more accurate
@@ -518,6 +530,9 @@ long percpu_counter_sum(struct percpu_co
 	spin_unlock(&fbc->lock);
 	return ret < 0 ? 0 : ret;
 }
+
+EXPORT_SYMBOL(percpu_counter_mod);
+EXPORT_SYMBOL(percpu_counter_mod_bh);
 EXPORT_SYMBOL(percpu_counter_sum);
 #endif
 
_