[PATCH v5 08/10] powerpc/smp: Allocate cpumask only after searching thread group

From: Srikar Dronamraju
Date: Mon Aug 10 2020 - 03:19:49 EST

If allocated earlier and the search fails, then cpu_l1_cache_map cpumask
is unnecessarily cleared. However cpu_l1_cache_map can be allocated /
cleared after we search thread group.

Please note CONFIG_CPUMASK_OFFSTACK is not set on Powerpc. Hence cpumask
allocated by zalloc_cpumask_var_node is never freed.

Cc: linuxppc-dev <linuxppc-dev@xxxxxxxxxxxxxxxx>
Cc: LKML <linux-kernel@xxxxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Anton Blanchard <anton@xxxxxxxxxx>
Cc: Oliver O'Halloran <oohall@xxxxxxxxx>
Cc: Nathan Lynch <nathanl@xxxxxxxxxxxxx>
Cc: Michael Neuling <mikey@xxxxxxxxxxx>
Cc: Gautham R Shenoy <ego@xxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Valentin Schneider <valentin.schneider@xxxxxxx>
Cc: Jordan Niethe <jniethe5@xxxxxxxxx>
Cc: Vaidyanathan Srinivasan <svaidy@xxxxxxxxxxxxx>
Reviewed-by: Gautham R. Shenoy <ego@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Changelog v4 ->v5:
Updated commit msg on why cpumask need not be freed.
(Michael Ellerman)

arch/powerpc/kernel/smp.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 7403fdcf3821..0536ac06876b 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -789,10 +789,6 @@ static int init_cpu_l1_cache_map(int cpu)
if (err)
goto out;

- zalloc_cpumask_var_node(&per_cpu(cpu_l1_cache_map, cpu),
- cpu_to_node(cpu));
cpu_group_start = get_cpu_thread_group_start(cpu, &tg);

if (unlikely(cpu_group_start == -1)) {
@@ -801,6 +797,9 @@ static int init_cpu_l1_cache_map(int cpu)
goto out;

+ zalloc_cpumask_var_node(&per_cpu(cpu_l1_cache_map, cpu),
+ GFP_KERNEL, cpu_to_node(cpu));
for (i = first_thread; i < first_thread + threads_per_core; i++) {
int i_group_start = get_cpu_thread_group_start(i, &tg);