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SubjectRe: [PATCH][2.5] Protect smp_call_function_data w/ spinlocks on Alpha
On Mon, 17 Feb 2003, Ivan Kokshaysky wrote:

> On Mon, Feb 17, 2003 at 03:32:09AM -0500, Zwane Mwaikambo wrote:
> > Assigns whatever the pointer happens to be at the time, be it NULL or the
> > next incoming message call.
>
> No, the pointer is guaranteed to be valid.
>
> > Therefore we'd need a lock to protect both the variable and critical
> > section.
>
> But smp_call_function_data pointer itself is exactly such a lock -
> other CPUs can't enter the section between 'if (pointer_lock())' and
> 'smp_call_function_data = 0', so there is no need for extra lock
> variable. Additionally, pointer_lock() with retry = 0 acts as spin_trylock.

Oh my mistake i thought you were talking about atomic assignment and not
blocking at that point. I misunderstood what you stated.

Zwane
--
function.linuxpower.ca
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