From: Roland Dreier Date: Fri, 14 Jul 2006 07:24:23 +0000 (-0700) Subject: [PATCH] Convert idr's internal locking to _irqsave variant X-Git-Tag: v2.6.18-rc2~40 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c259cc281255bdb30ceba190bfd7f37e3ae3fc85;p=linux-2.6 [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 Cc: Ingo Molnar Cc: Zach Brown , Signed-off-by: Roland Dreier Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/lib/idr.c b/lib/idr.c index 4d09681951..16d2143fea 100644 --- a/lib/idr.c +++ b/lib/idr.c @@ -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;