Re: tasklist_lock location
Thu, 1 Jul 1999 13:40:50 -0400 (EDT)

So, another question -- WHY isn't tasklist_lock exported to modules? If a
module were to iterate through all the tasks, wouldn't it need to use
read_(un)lock(tasklist_lock)? Or should I just loop through the tasks
without locking? I don't want to cause any problems with SMP mahcines here.

again, please CC to me. thanks.

c. chris erway

On Thu, 1 Jul 1999, Steve Dodd wrote:

> I've just woken up, so I might be about to talk crap, but:
> On UP, rwlock_t (which is what tasklist_lock is) is an empty structure, i.e.
> it takes no space. The macros that use it - {read,write}_{,un}lock - don't do
> anything on UP[1]. When compiled for SMP, the lock exists and the macros
> operate on it. AFAICS, tasklist_lock is not exported from the kernel anywhere
> - there needs to be an
> EXPORT_SYMBOL(tasklist_lock)
> somewhere for it to be visible from modules.
> I guess you need to submit a patch that adds that to the appropriate section
> of kernel/ksyms.c if you want your module to work with stock kernels. Otherwise,
> just add it to your local kernel.
> S.
> [1] As of 2.3.8ish, the macros reference the empty structure on UP even though
> they don't do anything, to avoid 'unused variable' messages. So your module
> won't work on UP either for 2.3.8+.

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