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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>
This commit is contained in:
Roland Dreier 2006-07-14 00:24:23 -07:00 committed by Linus Torvalds
parent 6fbe82a952
commit c259cc2812
1 changed files with 10 additions and 6 deletions
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16
lib/idr.c
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@ -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;