Andrew, Rusty,
Here is the patch which addresses RCU alloc problem araised by Rusty.
It replaced the mempool with Rusty's "RCU allocating RCU structure with
the object-to-be-freed together" solution. Patch is for 2.5.44-mm6,
compiled and tested.
Please review and apply if you like.
Mingming
--------------------------------------------------------------------------------
msg.c | 2 -
sem.c | 6 +--
shm.c | 2 -
util.c | 104
++++++++++++++++++++++++++++++++++-------------------------------
util.h | 23 ++++++++++----
5 files changed, 77 insertions(+), 60 deletions(-)
diff -urN 2544-mm6/ipc/msg.c 2544-mm6-ipc/ipc/msg.c
--- 2544-mm6/ipc/msg.c Mon Oct 28 09:51:20 2002
+++ 2544-mm6-ipc/ipc/msg.c Mon Oct 28 09:31:41 2002
@@ -93,7 +93,7 @@
int retval;
struct msg_queue *msq;
- msq = (struct msg_queue *) kmalloc (sizeof (*msq), GFP_KERNEL);
+ msq = (struct msg_queue *) ipc_rcu_alloc (sizeof (*msq));
if (!msq)
return -ENOMEM;
diff -urN 2544-mm6/ipc/sem.c 2544-mm6-ipc/ipc/sem.c
--- 2544-mm6/ipc/sem.c Mon Oct 28 09:51:20 2002
+++ 2544-mm6-ipc/ipc/sem.c Mon Oct 28 09:31:41 2002
@@ -126,7 +126,7 @@
return -ENOSPC;
size = sizeof (*sma) + nsems * sizeof (struct sem);
- sma = (struct sem_array *) ipc_alloc(size);
+ sma = (struct sem_array *) ipc_rcu_alloc(size);
if (!sma) {
return -ENOMEM;
}
@@ -138,14 +138,14 @@
sma->sem_perm.security = NULL;
retval = security_ops->sem_alloc_security(sma);
if (retval) {
- ipc_free(sma, size);
+ ipc_rcu_free(sma, size);
return retval;
}
id = ipc_addid(&sem_ids, &sma->sem_perm, sc_semmni);
if(id == -1) {
security_ops->sem_free_security(sma);
- ipc_free(sma, size);
+ ipc_rcu_free(sma, size);
return -ENOSPC;
}
used_sems += nsems;
diff -urN 2544-mm6/ipc/shm.c 2544-mm6-ipc/ipc/shm.c
--- 2544-mm6/ipc/shm.c Mon Oct 28 09:51:20 2002
+++ 2544-mm6-ipc/ipc/shm.c Mon Oct 28 09:31:41 2002
@@ -180,7 +180,7 @@
if (shm_tot + numpages >= shm_ctlall)
return -ENOSPC;
- shp = (struct shmid_kernel *) kmalloc (sizeof (*shp), GFP_USER);
+ shp = (struct shmid_kernel *) ipc_rcu_alloc (sizeof (*shp));
if (!shp)
return -ENOMEM;
diff -urN 2544-mm6/ipc/util.c 2544-mm6-ipc/ipc/util.c
--- 2544-mm6/ipc/util.c Mon Oct 28 09:51:20 2002
+++ 2544-mm6-ipc/ipc/util.c Mon Oct 28 09:38:52 2002
@@ -22,26 +22,11 @@
#include <linux/slab.h>
#include <linux/highuid.h>
#include <linux/security.h>
-#include <linux/mempool.h>
#if defined(CONFIG_SYSVIPC)
#include "util.h"
-static mempool_t* rcu_backup_pool;
-
-/* alloc and free function for rcu backup mempool */
-
-static void *alloc_ipc_rcu(int gfp_mask, void *pool_data)
-{
- return kmalloc(sizeof(struct rcu_ipc_free), gfp_mask);
-}
-
-static void free_ipc_rcu(void* arg, void *pool_data)
-{
- kfree(arg);
-}
-
/**
* ipc_init - initialise IPC subsystem
*
@@ -86,7 +71,7 @@
ids->seq_max = seq_limit;
}
- ids->entries = ipc_alloc(sizeof(struct ipc_id)*size);
+ ids->entries = ipc_rcu_alloc(sizeof(struct ipc_id)*size);
if(ids->entries == NULL) {
printk(KERN_ERR "ipc_init_ids() failed, ipc service disabled.\n");
@@ -94,13 +79,6 @@
}
for(i=0;i<ids->size;i++)
ids->entries[i].p = NULL;
-
- /* create a mempool in case normal kmalloc failed */
- rcu_backup_pool = mempool_create(MAX_RCU_BACKUPS,
- alloc_ipc_rcu, free_ipc_rcu, NULL);
-
- if (rcu_backup_pool == NULL)
- panic("ipc_init_ids() failed\n");
}
/**
@@ -128,6 +106,14 @@
return -1;
}
+static inline int use_vmalloc(int size)
+{
+ /* Too big for a single page? */
+ if (sizeof(struct ipc_rcu_kmalloc) + size > PAGE_SIZE)
+ return 1;
+ return 0;
+}
+
/*
* Requires ipc_ids.sem locked
*/
@@ -142,7 +128,7 @@
if(newsize <= ids->size)
return newsize;
- new = ipc_alloc(sizeof(struct ipc_id)*newsize);
+ new = ipc_rcu_alloc(sizeof(struct ipc_id)*newsize);
if(new == NULL)
return ids->size;
memcpy(new, ids->entries, sizeof(struct ipc_id)*ids->size);
@@ -257,16 +243,15 @@
out = kmalloc(size, GFP_KERNEL);
return out;
}
-
/**
- * ipc_free - free ipc space
+ * ipc_free - free ipc space
* @ptr: pointer returned by ipc_alloc
* @size: size of block
*
* Free a block created with ipc_alloc. The caller must know the size
* used in the allocation call.
*/
-
+
void ipc_free(void* ptr, int size)
{
if(size > PAGE_SIZE)
@@ -275,39 +260,60 @@
kfree(ptr);
}
-/*
- * Since RCU callback function is called in bh,
- * we need to defer the vfree to schedule_work
+/**
+ * ipc_rcu_alloc - allocate ipc and rcu space
+ * @size: size desired
+ *
+ * Allocate memory for the rcu header structure + the object.
+ * Returns the pointer to the object.
+ * NULL is returned if the allocation fails.
*/
-static void ipc_free_scheduled(void* arg)
-{
- struct rcu_ipc_free *a = arg;
- vfree(a->ptr);
- mempool_free(a, rcu_backup_pool);
-}
-
-static void ipc_free_callback(void* arg)
+
+void* ipc_rcu_alloc(int size)
{
- struct rcu_ipc_free *a = arg;
+ void* out;
/*
- * if data is vmalloced, then we need to delay the free
+ * We prepend the allocation with the rcu struct, and
+ * workqueue if necessary (for vmalloc).
*/
- if (a->size > PAGE_SIZE) {
- INIT_WORK(&a->work, ipc_free_scheduled, arg);
- schedule_work(&a->work);
+ if (use_vmalloc(size)) {
+ out = vmalloc(sizeof(struct ipc_rcu_vmalloc) + size);
+ if (out) out += sizeof(struct ipc_rcu_vmalloc);
} else {
- kfree(a->ptr);
- mempool_free(a, rcu_backup_pool);
+ out = kmalloc(sizeof(struct ipc_rcu_kmalloc)+size, GFP_KERNEL);
+ if (out) out += sizeof(struct ipc_rcu_kmalloc);
}
+
+ return out;
+}
+
+/**
+ * ipc_schedule_free - free ipc + rcu space
+ *
+ * Since RCU callback function is called in bh,
+ * we need to defer the vfree to schedule_work
+ */
+static void ipc_schedule_free(void* arg)
+{
+ struct ipc_rcu_vmalloc *free = arg;
+
+ INIT_WORK(&free->work, vfree, free);
+ schedule_work(&free->work);
}
void ipc_rcu_free(void* ptr, int size)
{
- struct rcu_ipc_free* arg = mempool_alloc(rcu_backup_pool, GFP_KERNEL);
+ if (use_vmalloc(size)) {
+ struct ipc_rcu_vmalloc *free;
+ free = ptr - sizeof(*free);
+ call_rcu(&free->rcu, ipc_schedule_free, free);
+ } else {
+ struct ipc_rcu_kmalloc *free;
+ free = ptr - sizeof(*free);
+ /* kfree takes a "const void *" so gcc warns. So we cast. */
+ call_rcu(&free->rcu, (void (*)(void *))kfree, free);
+ }
- arg->ptr = ptr;
- arg->size = size;
- call_rcu(&arg->rcu_head, ipc_free_callback, arg);
}
/**
diff -urN 2544-mm6/ipc/util.h 2544-mm6-ipc/ipc/util.h
--- 2544-mm6/ipc/util.h Mon Oct 28 09:51:20 2002
+++ 2544-mm6-ipc/ipc/util.h Mon Oct 28 09:37:43 2002
@@ -9,17 +9,24 @@
#define USHRT_MAX 0xffff
#define SEQ_MULTIPLIER (IPCMNI)
-#define MAX_RCU_BACKUPS 4 /*max # of elements in rcu_backup_pool*/
void sem_init (void);
void msg_init (void);
void shm_init (void);
-struct rcu_ipc_free {
- struct rcu_head rcu_head;
- void *ptr;
- int size;
- struct work_struct work;
+struct ipc_rcu_kmalloc
+{
+ struct rcu_head rcu;
+ /* "void *" makes sure alignment of following data is sane. */
+ void *data[0];
+};
+
+struct ipc_rcu_vmalloc
+{
+ struct rcu_head rcu;
+ struct work_struct work;
+ /* "void *" makes sure alignment of following data is sane. */
+ void *data[0];
};
struct ipc_ids {
@@ -52,6 +59,10 @@
*/
void* ipc_alloc(int size);
void ipc_free(void* ptr, int size);
+/* for allocation that need to be freed by RCU
+ * both function can sleep
+ */
+void* ipc_rcu_alloc(int size);
void ipc_rcu_free(void* arg, int size);
struct kern_ipc_perm* ipc_get(struct ipc_ids* ids, int id);
-
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