In my kernel module, firstly I wrote:

int alloc_device(const char *name, int number)
{
    char name[64];
    snprintf(name, sizeof(name), "worker%d", number);
    request_cache = kmem_cache_create(name, SECTOR_SIZE, 0, NULL, NULL);
    ......
}

In centos 7, this module works fine, but after port to centos 6, this kernel module reports:

kmem_cache_create: duplicate cache worker0
......

The key to this problme is in the implementation of kmem_cache_create() in 2.6.32 linux kernel (for centos 6):

struct kmem_cache *
kmem_cache_create (const char *name, size_t size, size_t align,
        unsigned long flags, void (*ctor)(void *))
{
        ......
        cachep->ctor = ctor;
        cachep->name = name;
......

After creating a new pool, it only point to ‘name’, not strdup() a new one. But the ‘name’ in my kernel module is a temporary variable (in stack), so it considers the name is “duplicated”.
The correct code should like:

static char *names[64];
/* before calling alloc_device() */
names = kcalloc(NR_OF_DEVICE, 64, GFP_KERNEL);
......
int alloc_device(const char *name, int number)
{
    snprintf(names[number], 64, "worker%d", number);
    request_cache = kmem_cache_create(names[number], SECTOR_SIZE, 0, NULL, NULL);
    ......
}

But why the old kernel module did not report error in centos 7? Because in centos 7 the default memory allocator is SLUB, and in centos 6 it is SLAB. They have totally different implementation.

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