[PATCH] Allow NULL pointers in percpu_free

The patch (as824b) makes percpu_free() ignore NULL arguments, as one would
expect for a deallocation routine.  (Note that free_percpu is #defined as
percpu_free in include/linux/percpu.h.) A few callers are updated to remove
now-unneeded tests for NULL.  A few other callers already seem to assume
that passing a NULL pointer to percpu_free() is okay!

The patch also removes an unnecessary NULL check in percpu_depopulate().
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/acpi/cstate.c

@@ -156,10 +156,8 @@ static int __init ffh_cstate_init(void)
 
 static void __exit ffh_cstate_exit(void)
 {
-	if (cpu_cstate_entry) {
 	free_percpu(cpu_cstate_entry);
 	cpu_cstate_entry = NULL;
-	}
 }
 
 arch_initcall(ffh_cstate_init);

block/blktrace.c

@@ -394,7 +394,6 @@ static int blk_trace_setup(request_queue_t *q, struct block_device *bdev,
 	if (bt) {
 		if (bt->dropped_file)
 			debugfs_remove(bt->dropped_file);
-		if (bt->sequence)
 		free_percpu(bt->sequence);
 		if (bt->rchan)
 			relay_close(bt->rchan);

mm/allocpercpu.c

@@ -17,10 +17,9 @@
 void percpu_depopulate(void *__pdata, int cpu)
 {
 	struct percpu_data *pdata = __percpu_disguise(__pdata);
-	if (pdata->ptrs[cpu]) {
+
 	kfree(pdata->ptrs[cpu]);
 	pdata->ptrs[cpu] = NULL;
-	}
 }
 EXPORT_SYMBOL_GPL(percpu_depopulate);
 
@@ -123,6 +122,8 @@ EXPORT_SYMBOL_GPL(__percpu_alloc_mask);
  */
 void percpu_free(void *__pdata)
 {
+	if (unlikely(!__pdata))
+		return;
 	__percpu_depopulate_mask(__pdata, &cpu_possible_map);
 	kfree(__percpu_disguise(__pdata));
 }

net/ipv6/af_inet6.c

@@ -720,9 +720,7 @@ snmp6_mib_free(void *ptr[2])
 {
 	if (ptr == NULL)
 		return;
-	if (ptr[0])
 	free_percpu(ptr[0]);
-	if (ptr[1])
 	free_percpu(ptr[1]);
 	ptr[0] = ptr[1] = NULL;
 }