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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: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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parent
6fbe82a952
commit
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16
lib/idr.c
16
lib/idr.c
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@ -38,14 +38,15 @@ static kmem_cache_t *idr_layer_cache;
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static struct idr_layer *alloc_layer(struct idr *idp)
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{
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struct idr_layer *p;
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unsigned long flags;
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spin_lock(&idp->lock);
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spin_lock_irqsave(&idp->lock, flags);
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if ((p = idp->id_free)) {
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idp->id_free = p->ary[0];
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idp->id_free_cnt--;
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p->ary[0] = NULL;
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}
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spin_unlock(&idp->lock);
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spin_unlock_irqrestore(&idp->lock, flags);
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return(p);
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}
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@ -59,12 +60,14 @@ static void __free_layer(struct idr *idp, struct idr_layer *p)
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static void free_layer(struct idr *idp, struct idr_layer *p)
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{
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unsigned long flags;
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/*
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* Depends on the return element being zeroed.
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*/
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spin_lock(&idp->lock);
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spin_lock_irqsave(&idp->lock, flags);
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__free_layer(idp, p);
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spin_unlock(&idp->lock);
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spin_unlock_irqrestore(&idp->lock, flags);
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}
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/**
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@ -168,6 +171,7 @@ static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
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{
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struct idr_layer *p, *new;
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int layers, v, id;
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unsigned long flags;
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id = starting_id;
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build_up:
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@ -191,14 +195,14 @@ static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
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* The allocation failed. If we built part of
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* the structure tear it down.
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*/
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spin_lock(&idp->lock);
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spin_lock_irqsave(&idp->lock, flags);
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for (new = p; p && p != idp->top; new = p) {
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p = p->ary[0];
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new->ary[0] = NULL;
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new->bitmap = new->count = 0;
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__free_layer(idp, new);
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}
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spin_unlock(&idp->lock);
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spin_unlock_irqrestore(&idp->lock, flags);
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return -1;
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}
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new->ary[0] = p;
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