Commit f6606cfd authored by Srikar Dronamraju's avatar Srikar Dronamraju Committed by Michael Ellerman
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powerpc/smp: Dont assume l2-cache to be superset of sibling 



Current code assumes that cpumask of cpus sharing a l2-cache mask will
always be a superset of cpu_sibling_mask.

Lets stop that assumption. cpu_l2_cache_mask is a superset of
cpu_sibling_mask if and only if shared_caches is set.

Reviewed-by: default avatarGautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200913171038.GB11808@linux.vnet.ibm.com
parent 3c6032a8

arch/powerpc/kernel/smp.c

+29 −14
Original line number Diff line number Diff line
@@ -1186,9 +1186,23 @@ static bool update_mask_by_l2(int cpu, struct cpumask *(*mask_fn)(int)) 
	int i;



	l2_cache = cpu_to_l2cache(cpu);

	if (!l2_cache)

	if (!l2_cache) {

		struct cpumask *(*sibling_mask)(int) = cpu_sibling_mask;



		/*

		 * If no l2cache for this CPU, assume all siblings to share

		 * cache with this CPU.

		 */

		if (has_big_cores)

			sibling_mask = cpu_smallcore_mask;



		for_each_cpu(i, sibling_mask(cpu))

			set_cpus_related(cpu, i, cpu_l2_cache_mask);



		return false;

	}



	cpumask_set_cpu(cpu, mask_fn(cpu));

	for_each_cpu(i, cpu_online_mask) {

		/*

		 * when updating the marks the current CPU has not been marked
@@ -1271,29 +1285,30 @@ static void add_cpu_to_masks(int cpu) 
	 * add it to it's own thread sibling mask.

	 */

	cpumask_set_cpu(cpu, cpu_sibling_mask(cpu));

	cpumask_set_cpu(cpu, cpu_core_mask(cpu));



	for (i = first_thread; i < first_thread + threads_per_core; i++)

		if (cpu_online(i))

			set_cpus_related(i, cpu, cpu_sibling_mask);



	add_cpu_to_smallcore_masks(cpu);

	/*

	 * Copy the thread sibling mask into the cache sibling mask

	 * and mark any CPUs that share an L2 with this CPU.

	 */

	for_each_cpu(i, cpu_sibling_mask(cpu))

		set_cpus_related(cpu, i, cpu_l2_cache_mask);

	update_mask_by_l2(cpu, cpu_l2_cache_mask);



	if (pkg_id == -1) {

		struct cpumask *(*mask)(int) = cpu_sibling_mask;



		/*

	 * Copy the cache sibling mask into core sibling mask and mark

	 * any CPUs on the same chip as this CPU.

		 * Copy the sibling mask into core sibling mask and

		 * mark any CPUs on the same chip as this CPU.

		 */

	for_each_cpu(i, cpu_l2_cache_mask(cpu))

		if (shared_caches)

			mask = cpu_l2_cache_mask;



		for_each_cpu(i, mask(cpu))

			set_cpus_related(cpu, i, cpu_core_mask);



	if (pkg_id == -1)

		return;

	}



	for_each_cpu(i, cpu_online_mask)

		if (get_physical_package_id(i) == pkg_id)

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