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Commit 196aa013 authored by Manfred Spraul's avatar Manfred Spraul Committed by Linus Torvalds
Browse files

ipc/util.c, ipc_rcu_alloc: cacheline align allocation 



Enforce that ipc_rcu_alloc returns a cacheline aligned pointer on SMP.

Rationale:

The SysV sem code tries to move the main spinlock into a seperate
cacheline (____cacheline_aligned_in_smp).  This works only if
ipc_rcu_alloc returns cacheline aligned pointers.  vmalloc and kmalloc
return cacheline algined pointers, the implementation of ipc_rcu_alloc
breaks that.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: default avatarManfred Spraul <manfred@colorfullife.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9ad66ae6

ipc/util.c

+6 −6
Original line number Diff line number Diff line
@@ -468,9 +468,7 @@ void ipc_free(void* ptr, int size) 
struct ipc_rcu {

	struct rcu_head rcu;

	atomic_t refcount;

	/* "void *" makes sure alignment of following data is sane. */

	void *data[0];

};

} ____cacheline_aligned_in_smp;



/**

 *	ipc_rcu_alloc	-	allocate ipc and rcu space
@@ -488,12 +486,14 @@ void *ipc_rcu_alloc(int size) 
	if (unlikely(!out))

		return NULL;

	atomic_set(&out->refcount, 1);

	return out->data;

	return out + 1;

}



int ipc_rcu_getref(void *ptr)

{

	return atomic_inc_not_zero(&container_of(ptr, struct ipc_rcu, data)->refcount);

	struct ipc_rcu *p = ((struct ipc_rcu *)ptr) - 1;



	return atomic_inc_not_zero(&p->refcount);

}



/**
@@ -507,7 +507,7 @@ static void ipc_schedule_free(struct rcu_head *head) 


void ipc_rcu_putref(void *ptr)

{

	struct ipc_rcu *p = container_of(ptr, struct ipc_rcu, data);

	struct ipc_rcu *p = ((struct ipc_rcu *)ptr) - 1;



	if (!atomic_dec_and_test(&p->refcount))

		return;