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Commit c259cc28 authored by Roland Dreier's avatar Roland Dreier Committed by Linus Torvalds
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[PATCH] Convert idr's internal locking to _irqsave variant 



Currently, the code in lib/idr.c uses a bare spin_lock(&idp->lock) to do
internal locking.  This is a nasty trap for code that might call idr
functions from different contexts; for example, it seems perfectly
reasonable to call idr_get_new() from process context and idr_remove() from
interrupt context -- but with the current locking this would lead to a
potential deadlock.

The simplest fix for this is to just convert the idr locking to use
spin_lock_irqsave().

In particular, this fixes a very complicated locking issue detected by
lockdep, involving the ib_ipoib driver's priv->lock and dev->_xmit_lock,
which get involved with the ib_sa module's query_idr.lock.

Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Zach Brown <zach.brown@oracle.com>,
Signed-off-by: default avatarRoland Dreier <rolandd@cisco.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 6fbe82a9

lib/idr.c

+10 −6
Original line number Diff line number Diff line
@@ -38,14 +38,15 @@ static kmem_cache_t *idr_layer_cache; 
static struct idr_layer *alloc_layer(struct idr *idp)

{

	struct idr_layer *p;

	unsigned long flags;



	spin_lock(&idp->lock);

	spin_lock_irqsave(&idp->lock, flags);

	if ((p = idp->id_free)) {

		idp->id_free = p->ary[0];

		idp->id_free_cnt--;

		p->ary[0] = NULL;

	}

	spin_unlock(&idp->lock);

	spin_unlock_irqrestore(&idp->lock, flags);

	return(p);

}
@@ -59,12 +60,14 @@ static void __free_layer(struct idr *idp, struct idr_layer *p) 


static void free_layer(struct idr *idp, struct idr_layer *p)

{

	unsigned long flags;



	/*

	 * Depends on the return element being zeroed.

	 */

	spin_lock(&idp->lock);

	spin_lock_irqsave(&idp->lock, flags);

	__free_layer(idp, p);

	spin_unlock(&idp->lock);

	spin_unlock_irqrestore(&idp->lock, flags);

}



/**
@@ -168,6 +171,7 @@ static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id) 
{

	struct idr_layer *p, *new;

	int layers, v, id;

	unsigned long flags;



	id = starting_id;

build_up:
@@ -191,14 +195,14 @@ build_up: 
			 * The allocation failed.  If we built part of

			 * the structure tear it down.

			 */

			spin_lock(&idp->lock);

			spin_lock_irqsave(&idp->lock, flags);

			for (new = p; p && p != idp->top; new = p) {

				p = p->ary[0];

				new->ary[0] = NULL;

				new->bitmap = new->count = 0;

				__free_layer(idp, new);

			}

			spin_unlock(&idp->lock);

			spin_unlock_irqrestore(&idp->lock, flags);

			return -1;

		}

		new->ary[0] = p;