memstick: avert possible race condition between idr_pre_get and idr_get_new
Alex Dubov [Thu, 13 Jan 2011 01:01:04 +0000 (17:01 -0800)]
Implement the usual pattern around idr_pre_get() and idr_get_new() to
handlethe situation where another thread concurrently steals this thread's
idr_pre_get() preallocation.

Signed-off-by: Alex Dubov <oakad@yahoo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/memstick/core/memstick.c
drivers/memstick/core/mspro_block.c

index 4303b7e..e9a3eab 100644 (file)
@@ -511,14 +511,18 @@ int memstick_add_host(struct memstick_host *host)
 {
        int rc;
 
-       if (!idr_pre_get(&memstick_host_idr, GFP_KERNEL))
-               return -ENOMEM;
+       while (1) {
+               if (!idr_pre_get(&memstick_host_idr, GFP_KERNEL))
+                       return -ENOMEM;
 
-       spin_lock(&memstick_host_lock);
-       rc = idr_get_new(&memstick_host_idr, host, &host->id);
-       spin_unlock(&memstick_host_lock);
-       if (rc)
-               return rc;
+               spin_lock(&memstick_host_lock);
+               rc = idr_get_new(&memstick_host_idr, host, &host->id);
+               spin_unlock(&memstick_host_lock);
+               if (!rc)
+                       break;
+               else if (rc != -EAGAIN)
+                       return rc;
+       }
 
        dev_set_name(&host->dev, "memstick%u", host->id);
 
index 02362ec..a167938 100644 (file)
@@ -1206,10 +1206,12 @@ static int mspro_block_init_disk(struct memstick_dev *card)
 
        msb->page_size = be16_to_cpu(sys_info->unit_size);
 
-       if (!idr_pre_get(&mspro_block_disk_idr, GFP_KERNEL))
+       mutex_lock(&mspro_block_disk_lock);
+       if (!idr_pre_get(&mspro_block_disk_idr, GFP_KERNEL)) {
+               mutex_unlock(&mspro_block_disk_lock);
                return -ENOMEM;
+       }
 
-       mutex_lock(&mspro_block_disk_lock);
        rc = idr_get_new(&mspro_block_disk_idr, card, &disk_id);
        mutex_unlock(&mspro_block_disk_lock);