From: Chris Mason <chris.mason@oracle.com>
Date: Tue, 5 Jul 2011 19:07:26 +0000 (-0500)
Subject: use rwlocks for ipc
X-Git-Tag: v2.6.39-400.9.0~944
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=78fe45325c8e2e3f4b6ebb1ee15b6c2e8af5ddb1;p=users%2Fjedix%2Flinux-maple.git

use rwlocks for ipc

Signed-off-by: Chris Mason <chris.mason@oracle.com>
---

diff --git a/include/linux/ipc.h b/include/linux/ipc.h
index 3b1594d662b02..e7def7b18e8ab 100644
--- a/include/linux/ipc.h
+++ b/include/linux/ipc.h
@@ -85,7 +85,7 @@ struct ipc_kludge {
 /* used by in-kernel data structures */
 struct kern_ipc_perm
 {
-	spinlock_t	lock;
+	rwlock_t	lock;
 	int		deleted;
 	int		id;
 	key_t		key;
diff --git a/ipc/sem.c b/ipc/sem.c
index d34316d8a9244..2df779307fb58 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -95,6 +95,7 @@
 #define sem_ids(ns)	((ns)->ids[IPC_SEM_IDS])
 
 #define sem_unlock(sma)		ipc_unlock(&(sma)->sem_perm)
+#define sem_read_unlock(sma)	ipc_read_unlock(&(sma)->sem_perm)
 #define sem_checkid(sma, semid)	ipc_checkid(&sma->sem_perm, semid)
 
 static int newary(struct ipc_namespace *, struct ipc_params *);
@@ -171,6 +172,17 @@ static inline struct sem_array *sem_lock_check(struct ipc_namespace *ns,
 	return container_of(ipcp, struct sem_array, sem_perm);
 }
 
+static inline struct sem_array *sem_read_lock_check(struct ipc_namespace *ns,
+							int id)
+{
+	struct kern_ipc_perm *ipcp = ipc_read_lock_check(&sem_ids(ns), id);
+
+	if (IS_ERR(ipcp))
+		return (struct sem_array *)ipcp;
+
+	return container_of(ipcp, struct sem_array, sem_perm);
+}
+
 static inline void sem_lock_and_putref(struct sem_array *sma)
 {
 	ipc_lock_by_ptr(&sma->sem_perm);
@@ -183,11 +195,17 @@ static inline void sem_getref_and_unlock(struct sem_array *sma)
 	ipc_unlock(&(sma)->sem_perm);
 }
 
+static inline void sem_getref_and_read_unlock(struct sem_array *sma)
+{
+	ipc_rcu_getref(sma);
+	ipc_read_unlock(&(sma)->sem_perm);
+}
+
 static inline void sem_putref(struct sem_array *sma)
 {
-	ipc_lock_by_ptr(&sma->sem_perm);
+	rcu_read_lock();
 	ipc_rcu_putref(sma);
-	ipc_unlock(&(sma)->sem_perm);
+	rcu_read_unlock();
 }
 
 static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
@@ -775,7 +793,7 @@ static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 	int i;
 
 	/* Free the existing undo structures for this semaphore set.  */
-	assert_spin_locked(&sma->sem_perm.lock);
+	//assert_spin_locked(&sma->sem_perm.lock);
 	list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
 		list_del(&un->list_id);
 		spin_lock(&un->ulp->lock);
@@ -1020,7 +1038,7 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
 			spin_unlock(&curr->lock);
 		}
 
-		assert_spin_locked(&sma->sem_perm.lock);
+		//assert_spin_locked(&sma->sem_perm.lock);
 		list_for_each_entry(un, &sma->list_id, list_id) {
 			for (i = 0; i < nsems; i++)
 				un->semadj[i] = 0;
@@ -1062,7 +1080,7 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
 		if (val > SEMVMX || val < 0)
 			goto out_unlock;
 
-		assert_spin_locked(&sma->sem_perm.lock);
+		//assert_spin_locked(&sma->sem_perm.lock);
 		list_for_each_entry(un, &sma->list_id, list_id)
 			un->semadj[semnum] = 0;
 
@@ -1334,7 +1352,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
 	new->semid = semid;
 	assert_spin_locked(&ulp->lock);
 	list_add_rcu(&new->list_proc, &ulp->list_proc);
-	assert_spin_locked(&sma->sem_perm.lock);
+	//assert_spin_locked(&sma->sem_perm.lock);
 	list_add(&new->list_id, &sma->list_id);
 	un = new;
 
@@ -1507,7 +1525,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
 
 	INIT_LIST_HEAD(&tasks);
 
-	sma = sem_lock_check(ns, semid);
+	sma = sem_read_lock_check(ns, semid);
 	if (IS_ERR(sma)) {
 		if (un)
 			rcu_read_unlock();
@@ -1558,7 +1576,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
 	 * per-semaphore locks instead.
 	 */
 	if (!un)
-		sem_getref_and_unlock(sma);
+		sem_getref_and_read_unlock(sma);
 
 	error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current),
 				  &pending, &blocker);
@@ -1602,7 +1620,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
 	spin_unlock(&blocker->lock);
 
 	if (un)
-		sem_getref_and_unlock(sma);
+		sem_getref_and_read_unlock(sma);
 
 	if (timeout)
 		jiffies_left = schedule_timeout(jiffies_left);
@@ -1679,7 +1697,7 @@ out_putref:
 	goto out_wakeup;
 
 out_unlock_free:
-	sem_unlock(sma);
+	sem_read_unlock(sma);
 out_wakeup:
 	wake_up_sem_queue_do(&tasks);
 out_free:
@@ -1777,7 +1795,7 @@ void exit_sem(struct task_struct *tsk)
 		}
 
 		/* remove un from the linked lists */
-		assert_spin_locked(&sma->sem_perm.lock);
+		//assert_spin_locked(&sma->sem_perm.lock);
 		list_del(&un->list_id);
 
 		spin_lock(&ulp->lock);
diff --git a/ipc/util.c b/ipc/util.c
index 5c0d28921ba8c..d60930ed0285b 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -259,14 +259,14 @@ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 	if (ids->in_use >= size)
 		return -ENOSPC;
 
-	spin_lock_init(&new->lock);
+	rwlock_init(&new->lock);
 	new->deleted = 0;
 	rcu_read_lock();
-	spin_lock(&new->lock);
+	write_lock(&new->lock);
 
 	err = idr_get_new(&ids->ipcs_idr, new, &id);
 	if (err) {
-		spin_unlock(&new->lock);
+		write_unlock(&new->lock);
 		rcu_read_unlock();
 		return err;
 	}
@@ -481,7 +481,7 @@ void ipc_free(void* ptr, int size)
  */
 struct ipc_rcu_hdr
 {
-	int refcount;
+	atomic_t refcount;
 	int is_vmalloc;
 	void *data[0];
 };
@@ -535,14 +535,14 @@ void* ipc_rcu_alloc(int size)
 		if (out) {
 			out += HDRLEN_VMALLOC;
 			container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 1;
-			container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
+			atomic_set(&container_of(out, struct ipc_rcu_hdr, data)->refcount, 1);
 		}
 	} else {
 		out = kmalloc(HDRLEN_KMALLOC + size, GFP_KERNEL);
 		if (out) {
 			out += HDRLEN_KMALLOC;
 			container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 0;
-			container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
+			atomic_set(&container_of(out, struct ipc_rcu_hdr, data)->refcount, 1);
 		}
 	}
 
@@ -551,7 +551,7 @@ void* ipc_rcu_alloc(int size)
 
 void ipc_rcu_getref(void *ptr)
 {
-	container_of(ptr, struct ipc_rcu_hdr, data)->refcount++;
+	atomic_inc(&container_of(ptr, struct ipc_rcu_hdr, data)->refcount);
 }
 
 static void ipc_do_vfree(struct work_struct *work)
@@ -594,7 +594,7 @@ static void ipc_immediate_free(struct rcu_head *head)
 
 void ipc_rcu_putref(void *ptr)
 {
-	if (--container_of(ptr, struct ipc_rcu_hdr, data)->refcount > 0)
+	if (!atomic_dec_and_test(&container_of(ptr, struct ipc_rcu_hdr, data)->refcount))
 		return;
 
 	if (container_of(ptr, struct ipc_rcu_hdr, data)->is_vmalloc) {
@@ -707,13 +707,39 @@ struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
 		return ERR_PTR(-EINVAL);
 	}
 
-	spin_lock(&out->lock);
+	write_lock(&out->lock);
 	
 	/* ipc_rmid() may have already freed the ID while ipc_lock
 	 * was spinning: here verify that the structure is still valid
 	 */
 	if (out->deleted) {
-		spin_unlock(&out->lock);
+		write_unlock(&out->lock);
+		rcu_read_unlock();
+		return ERR_PTR(-EINVAL);
+	}
+
+	return out;
+}
+
+struct kern_ipc_perm *ipc_read_lock(struct ipc_ids *ids, int id)
+{
+	struct kern_ipc_perm *out;
+	int lid = ipcid_to_idx(id);
+
+	rcu_read_lock();
+	out = idr_find(&ids->ipcs_idr, lid);
+	if (out == NULL) {
+		rcu_read_unlock();
+		return ERR_PTR(-EINVAL);
+	}
+
+	read_lock(&out->lock);
+	
+	/* ipc_rmid() may have already freed the ID while ipc_lock
+	 * was spinning: here verify that the structure is still valid
+	 */
+	if (out->deleted) {
+		read_unlock(&out->lock);
 		rcu_read_unlock();
 		return ERR_PTR(-EINVAL);
 	}
@@ -737,6 +763,22 @@ struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id)
 	return out;
 }
 
+struct kern_ipc_perm *ipc_read_lock_check(struct ipc_ids *ids, int id)
+{
+	struct kern_ipc_perm *out;
+
+	out = ipc_read_lock(ids, id);
+	if (IS_ERR(out))
+		return out;
+
+	if (ipc_checkid(out, id)) {
+		ipc_read_unlock(out);
+		return ERR_PTR(-EIDRM);
+	}
+
+	return out;
+}
+
 /**
  * ipcget - Common sys_*get() code
  * @ns : namsepace
diff --git a/ipc/util.h b/ipc/util.h
index 6f5c20bedaab2..25e9808bac683 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -161,16 +161,23 @@ static inline int ipc_checkid(struct kern_ipc_perm *ipcp, int uid)
 static inline void ipc_lock_by_ptr(struct kern_ipc_perm *perm)
 {
 	rcu_read_lock();
-	spin_lock(&perm->lock);
+	write_lock(&perm->lock);
 }
 
 static inline void ipc_unlock(struct kern_ipc_perm *perm)
 {
-	spin_unlock(&perm->lock);
+	write_unlock(&perm->lock);
+	rcu_read_unlock();
+}
+
+static inline void ipc_read_unlock(struct kern_ipc_perm *perm)
+{
+	read_unlock(&perm->lock);
 	rcu_read_unlock();
 }
 
 struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id);
+struct kern_ipc_perm *ipc_read_lock_check(struct ipc_ids *ids, int id);
 int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
 			struct ipc_ops *ops, struct ipc_params *params);
 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,