Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 32fcfd40 authored by Al Viro's avatar Al Viro
Browse files

make vfree() safe to call from interrupt contexts 



A bunch of RCU callbacks want to be able to do vfree() and end up with
rather kludgy schemes.  Just let vfree() do the right thing - put the
victim on llist and schedule actual __vunmap() via schedule_work(), so
that it runs from non-interrupt context.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 6dbe51c2

mm/vmalloc.c

+40 −5
Original line number Diff line number Diff line
@@ -27,10 +27,30 @@ 
#include <linux/pfn.h>

#include <linux/kmemleak.h>

#include <linux/atomic.h>

#include <linux/llist.h>

#include <asm/uaccess.h>

#include <asm/tlbflush.h>

#include <asm/shmparam.h>



struct vfree_deferred {

	struct llist_head list;

	struct work_struct wq;

};

static DEFINE_PER_CPU(struct vfree_deferred, vfree_deferred);



static void __vunmap(const void *, int);



static void free_work(struct work_struct *w)

{

	struct vfree_deferred *p = container_of(w, struct vfree_deferred, wq);

	struct llist_node *llnode = llist_del_all(&p->list);

	while (llnode) {

		void *p = llnode;

		llnode = llist_next(llnode);

		__vunmap(p, 1);

	}

}



/*** Page table manipulation functions ***/



static void vunmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end)
@@ -1184,10 +1204,14 @@ void __init vmalloc_init(void) 


	for_each_possible_cpu(i) {

		struct vmap_block_queue *vbq;

		struct vfree_deferred *p;



		vbq = &per_cpu(vmap_block_queue, i);

		spin_lock_init(&vbq->lock);

		INIT_LIST_HEAD(&vbq->free);

		p = &per_cpu(vfree_deferred, i);

		init_llist_head(&p->list);

		INIT_WORK(&p->wq, free_work);

	}



	/* Import existing vmlist entries. */
@@ -1520,14 +1544,24 @@ static void __vunmap(const void *addr, int deallocate_pages) 
 *	obtained from vmalloc(), vmalloc_32() or __vmalloc(). If @addr is

 *	NULL, no operation is performed.

 *

 *	Must not be called in interrupt context.

 *	Must not be called in NMI context (strictly speaking, only if we don't

 *	have CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG, but making the calling

 *	conventions for vfree() arch-depenedent would be a really bad idea)

 *	

 */

void vfree(const void *addr)

{

	BUG_ON(in_interrupt());

	BUG_ON(in_nmi());



	kmemleak_free(addr);



	if (!addr)

		return;

	if (unlikely(in_interrupt())) {

		struct vfree_deferred *p = &__get_cpu_var(vfree_deferred);

		llist_add((struct llist_node *)addr, &p->list);

		schedule_work(&p->wq);

	} else

		__vunmap(addr, 1);

}

EXPORT_SYMBOL(vfree);
@@ -1545,6 +1579,7 @@ void vunmap(const void *addr) 
{

	BUG_ON(in_interrupt());

	might_sleep();

	if (addr)

		__vunmap(addr, 0);

}

EXPORT_SYMBOL(vunmap);