[PATCH] Convert idr's internal locking to _irqsave variant (c259cc28) · Commits · 戴 / test

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:

Roland Dreier <rolandd@cisco.com> Signed-off-by:

Andrew Morton <akpm@osdl.org> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

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;

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