Re: [PATCH 2/2] spinlock_debug: Print kallsyms name for lock

From: Andrew Morton
Date: Mon Apr 23 2012 - 17:54:43 EST

On Mon, 23 Apr 2012 14:45:25 -0700
Stephen Boyd <sboyd@xxxxxxxxxxxxxx> wrote:

> When a spinlock warning is printed we usually get
> BUG: spinlock bad magic on CPU#0, modprobe/111
> lock: 0xdff09f38, .magic: 00000000, .owner: /0, .owner_cpu: 0
> but it's nicer to print the symbol for the lock if we have it so
> that we can avoid 'grep dff09f38 /proc/kallsyms' to find out
> which lock it was. Use kallsyms to print the symbol name so we
> get something a bit easier to read
> BUG: spinlock bad magic on CPU#0, modprobe/112
> lock: test_lock, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
> If the lock is not in kallsyms %ps will fall back to printing the address
> directly.

hm. Is this true? From my reading of kallsyms_lookup(), it will fall
into module_address_lookup() whcih is a no-op if !CONFIG_MODULES.

> --- a/lib/spinlock_debug.c
> +++ b/lib/spinlock_debug.c
> @@ -58,7 +58,7 @@ static void spin_dump(raw_spinlock_t *lock, const char *msg)
> printk(KERN_EMERG "BUG: spinlock %s on CPU#%d, %s/%d\n",
> msg, raw_smp_processor_id(),
> current->comm, task_pid_nr(current));
> - printk(KERN_EMERG " lock: %p, .magic: %08x, .owner: %s/%d, "
> + printk(KERN_EMERG " lock: %ps, .magic: %08x, .owner: %s/%d, "
> ".owner_cpu: %d\n",
> lock, lock->magic,
> owner ? owner->comm : "<none>",

Maybe. It will only do useful things for statically-allocated locks
which are rare and which we are unlikely to screw up as easily as locks
which lie in dynamically allocated memory.
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