[bug report] habanalabs: add debugfs support

[Dan Carpenter]

Hello Oded Gabbay,

The patch c216477363a3: "habanalabs: add debugfs support" from Feb
16, 2019, leads to the following Smatch static checker warning:

	drivers/accel/habanalabs/common/debugfs.c:272 vm_show()
	warn: sleeping in atomic context

drivers/accel/habanalabs/common/debugfs.c
    241 static int vm_show(struct seq_file *s, void *data)
    242 {
    243         struct hl_debugfs_entry *entry = s->private;
    244         struct hl_dbg_device_entry *dev_entry = entry->dev_entry;
    245         struct hl_vm_hw_block_list_node *lnode;
    246         struct hl_ctx *ctx;
    247         struct hl_vm *vm;
    248         struct hl_vm_hash_node *hnode;
    249         struct hl_userptr *userptr;
    250         struct hl_vm_phys_pg_pack *phys_pg_pack = NULL;
    251         struct hl_va_range *va_range;
    252         struct hl_vm_va_block *va_block;
    253         enum vm_type *vm_type;
    254         bool once = true;
    255         u64 j;
    256         int i;
    257 
    258         if (!dev_entry->hdev->mmu_enable)
    259                 return 0;
    260 
    261         spin_lock(&dev_entry->ctx_mem_hash_spinlock);
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This is holding a spinlock.

    262 
    263         list_for_each_entry(ctx, &dev_entry->ctx_mem_hash_list, debugfs_list) {
    264                 once = false;
    265                 seq_puts(s, "\n\n----------------------------------------------------");
    266                 seq_puts(s, "\n----------------------------------------------------\n\n");
    267                 seq_printf(s, "ctx asid: %u\n", ctx->asid);
    268 
    269                 seq_puts(s, "\nmappings:\n\n");
    270                 seq_puts(s, "    virtual address        size          handle\n");
    271                 seq_puts(s, "----------------------------------------------------\n");
--> 272                 mutex_lock(&ctx->mem_hash_lock);
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
so it can't take a mutex or it leads to a sleeping in atomic bug.  These
can be detected at runtime by enabling CONFIG_DEBUG_ATOMIC_SLEEP.

regards,
dan carpenter