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 <[EMAIL PROTECTED]>
Cc: Ingo Molnar <[EMAIL PROTECTED]>
Cc: Zach Brown <[EMAIL PROTECTED]>,
Signed-off-by: Roland Dreier <[EMAIL PROTECTED]>
---
diff --git a/lib/idr.c b/lib/idr.c
index 4d09681..16d2143 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
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
{
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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