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DateMon, 8 Jun 2009 16:05:25 -0700
FromAndrew Morton <>
SubjectRe: [Patch 02/12] GRU - add user request to explicitly unload a gru context
On Mon, 08 Jun 2009 12:16:50 -0500
steiner@sgi.com wrote:

> /*
> + * Free all kernel contexts that are not currently in use.
> + * Returns 0 if all freed, else number of inuse context.
> + */
> +static int gru_free_kernel_contexts(void)
> +{
> + struct gru_blade_state *bs;
> + struct gru_thread_state *kgts;
> + int bid, ret = 0;
> +
> + for (bid = 0; bid < GRU_MAX_BLADES; bid++) {
> + bs = gru_base[bid];
> + if (!bs)
> + continue;
> + if (down_write_trylock(&bs->bs_kgts_sema)) {

trylocks are always lame - they add a rarely-executed code path where
bugs can lurk. They're often an admission that the locking is screwed
up.

I don't know if the latter is true here, but it would be helpful to add
a comment explaining what's going on, and why this unusual and
troublesome locking primitive is being used.

> + kgts = bs->bs_kgts;
> + if (kgts && kgts->ts_gru)
> + gru_unload_context(kgts, 0);
> + kfree(kgts);
> + bs->bs_kgts = NULL;
> + up_write(&bs->bs_kgts_sema);

nit: the kfree() can be moved outside the locked region.

> + } else {
> + ret++;
> + }
> + }
> + return ret;
> +}


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