The patch titled
idr: make idr_remove rcu-safe
has been added to the -mm tree. Its filename is
idr-make-idr_remove-rcu-safe.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: idr: make idr_remove rcu-safe
From: Nadia Derbey <Nadia.Derbey@xxxxxxxx>
Introduce the free_layer() routine: it is the one that actually frees memory
after a grace period has elapsed.
Signed-off-by: Nadia Derbey <Nadia.Derbey@xxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Cc: Jim Houston <jim.houston@xxxxxxxxxxx>
Cc: Pierre Peiffer <peifferp@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/idr.c | 57 +++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 43 insertions(+), 14 deletions(-)
diff -puN lib/idr.c~idr-make-idr_remove-rcu-safe lib/idr.c
--- a/lib/idr.c~idr-make-idr_remove-rcu-safe
+++ a/lib/idr.c
@@ -52,6 +52,19 @@ static struct idr_layer *get_from_free_l
return(p);
}
+static void idr_layer_rcu_free(struct rcu_head *head)
+{
+ struct idr_layer *layer;
+
+ layer = container_of(head, struct idr_layer, rcu_head);
+ kmem_cache_free(idr_layer_cache, layer);
+}
+
+static inline void free_layer(struct idr_layer *p)
+{
+ call_rcu(&p->rcu_head, idr_layer_rcu_free);
+}
+
/* only called when idp->lock is held */
static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
{
@@ -334,6 +347,7 @@ static void sub_remove(struct idr *idp,
struct idr_layer *p = idp->top;
struct idr_layer **pa[MAX_LEVEL];
struct idr_layer ***paa = &pa[0];
+ struct idr_layer *to_free;
int n;
*paa = NULL;
@@ -349,13 +363,18 @@ static void sub_remove(struct idr *idp,
n = id & IDR_MASK;
if (likely(p != NULL && test_bit(n, &p->bitmap))){
__clear_bit(n, &p->bitmap);
- p->ary[n] = NULL;
+ rcu_assign_pointer(p->ary[n], NULL);
+ to_free = NULL;
while(*paa && ! --((**paa)->count)){
- move_to_free_list(idp, **paa);
+ if (to_free)
+ free_layer(to_free);
+ to_free = **paa;
**paa-- = NULL;
}
if (!*paa)
idp->layers = 0;
+ if (to_free)
+ free_layer(to_free);
} else
idr_remove_warning(id);
}
@@ -368,22 +387,34 @@ static void sub_remove(struct idr *idp,
void idr_remove(struct idr *idp, int id)
{
struct idr_layer *p;
+ struct idr_layer *to_free;
/* Mask off upper bits we don't use for the search. */
id &= MAX_ID_MASK;
sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
- idp->top->ary[0]) { // We can drop a layer
-
+ idp->top->ary[0]) {
+ /*
+ * Single child at leftmost slot: we can shrink the tree.
+ * This level is not needed anymore since when layers are
+ * inserted, they are inserted at the top of the existing
+ * tree.
+ */
+ to_free = idp->top;
p = idp->top->ary[0];
- idp->top->bitmap = idp->top->count = 0;
- move_to_free_list(idp, idp->top);
- idp->top = p;
+ rcu_assign_pointer(idp->top, p);
--idp->layers;
+ to_free->bitmap = to_free->count = 0;
+ free_layer(to_free);
}
while (idp->id_free_cnt >= IDR_FREE_MAX) {
p = get_from_free_list(idp);
+ /*
+ * Note: we don't call the rcu callback here, since the only
+ * layers that fall into the freelist are those that have been
+ * preallocated.
+ */
kmem_cache_free(idr_layer_cache, p);
}
return;
@@ -424,15 +455,13 @@ void idr_remove_all(struct idr *idp)
id += 1 << n;
while (n < fls(id)) {
- if (p) {
- memset(p, 0, sizeof *p);
- move_to_free_list(idp, p);
- }
+ if (p)
+ free_layer(p);
n += IDR_BITS;
p = *--paa;
}
}
- idp->top = NULL;
+ rcu_assign_pointer(idp->top, NULL);
idp->layers = 0;
}
EXPORT_SYMBOL(idr_remove_all);
@@ -549,7 +578,7 @@ EXPORT_SYMBOL(idr_for_each);
* A -ENOENT return indicates that @id was not found.
* A -EINVAL return indicates that @id was not within valid constraints.
*
- * The caller must serialize vs idr_find(), idr_get_new(), and idr_remove().
+ * The caller must serialize with writers.
*/
void *idr_replace(struct idr *idp, void *ptr, int id)
{
@@ -575,7 +604,7 @@ void *idr_replace(struct idr *idp, void
return ERR_PTR(-ENOENT);
old_p = p->ary[n];
- p->ary[n] = ptr;
+ rcu_assign_pointer(p->ary[n], ptr);
return old_p;
}
_
Patches currently in -mm which might be from Nadia.Derbey@xxxxxxxx are
idr-change-the-idr-structure.patch
idr-rename-some-of-the-idr-apis-internal-routines.patch
idr-fix-a-printk-call.patch
idr-error-checking-factorization.patch
idr-make-idr_get_new-rcu-safe.patch
idr-make-idr_find-rcu-safe.patch
idr-make-idr_remove-rcu-safe.patch
ipc-call-idr_find-without-locking-in-ipc_lock.patch
ipc-get-rid-of-ipc_lock_down.patch
--
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