path: root/ipc/util.h
diff options
authorNadia Derbey <Nadia.Derbey@bull.net>2007-10-18 23:40:54 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-19 11:53:48 -0700
commit3e148c79938aa39035669c1cfa3ff60722134535 (patch)
tree0effb3edfece56ea38a9727ec8f4721d9a4c3ea8 /ipc/util.h
parentf4566f04854d78acfc74b9acb029744acde9d033 (diff)
fix idr_find() locking
This is a patch that fixes the way idr_find() used to be called in ipc_lock(): in all the paths that don't imply an update of the ipcs idr, it was called without the idr tree being locked. The changes are: . in ipc_ids, the mutex has been changed into a reader/writer semaphore. . ipc_lock() now takes the mutex as a reader during the idr_find(). . a new routine ipc_lock_down() has been defined: it doesn't take the mutex, assuming that it is being held by the caller. This is the routine that is now called in all the update paths. Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net> Acked-by: Jarek Poplawski <jarkao2@o2.pl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc/util.h')
1 files changed, 26 insertions, 2 deletions
diff --git a/ipc/util.h b/ipc/util.h
index 99414a36a25..bd47687077e 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -32,7 +32,7 @@ struct ipc_ids {
int in_use;
unsigned short seq;
unsigned short seq_max;
- struct mutex mutex;
+ struct rw_semaphore rw_mutex;
struct idr ipcs_idr;
@@ -81,8 +81,10 @@ void __init ipc_init_proc_interface(const char *path, const char *header,
#define ipcid_to_idx(id) ((id) % SEQ_MULTIPLIER)
-/* must be called with ids->mutex acquired.*/
+/* must be called with ids->rw_mutex acquired for writing */
int ipc_addid(struct ipc_ids *, struct kern_ipc_perm *, int);
+/* must be called with ids->rw_mutex acquired for reading */
int ipc_get_maxid(struct ipc_ids *);
/* must be called with both locks acquired. */
@@ -107,6 +109,11 @@ void* ipc_rcu_alloc(int size);
void ipc_rcu_getref(void *ptr);
void ipc_rcu_putref(void *ptr);
+ * ipc_lock_down: called with rw_mutex held
+ * ipc_lock: called without that lock held
+ */
+struct kern_ipc_perm *ipc_lock_down(struct ipc_ids *, int);
struct kern_ipc_perm *ipc_lock(struct ipc_ids *, int);
void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out);
@@ -155,6 +162,23 @@ static inline void ipc_unlock(struct kern_ipc_perm *perm)
+static inline struct kern_ipc_perm *ipc_lock_check_down(struct ipc_ids *ids,
+ int id)
+ struct kern_ipc_perm *out;
+ out = ipc_lock_down(ids, id);
+ if (IS_ERR(out))
+ return out;
+ if (ipc_checkid(ids, out, id)) {
+ ipc_unlock(out);
+ return ERR_PTR(-EIDRM);
+ }
+ return out;
static inline struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids,
int id)