Introduce the infrastructure function housekeeping_update() to modify housekeeping_cpumask at runtime and update the configurations of dependent subsystems accordingly in following patches. Parent patch: sched/isolation: Exclude dynamically isolated CPUs from housekeeping masks https://lore.kernel.org/lkml/20240821142312.236970-1-longman@xxxxxxxxxx/ Signed-off-by: Costa Shulyupin <costa.shul@xxxxxxxxxx> --- Note: In theory, updating housekeeping.flags only once is possible. However, this approach would make this and following code less clear and harder to follow and review. Changes in v3: - Remove redundant WRITE_ONCE. The first WRITE_ONCE is located in housekeeping_update() because this function will update dependent subsystems with changes of the housekeeping masks. Changes in v2: - remove unnecessary `err` variable - add for_each_clear_bit... to clear isolated CPUs - Address Gleixner's comments: - use WRITE_ONCE to change housekeeping.flags - use `struct cpumask *update` in signature of housekeeping_update v1: - https://lore.kernel.org/lkml/20240516190437.3545310-2-costa.shul@xxxxxxxxxx/ --- kernel/sched/isolation.c | 43 ++++++++++++++++++++++++++++++++++++---- 1 file changed, 39 insertions(+), 4 deletions(-) diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index 2ee47bc25aea..ebbb215505e8 100644 --- a/kernel/sched/isolation.c +++ b/kernel/sched/isolation.c @@ -127,6 +127,40 @@ static void __init housekeeping_setup_type(enum hk_type type, housekeeping_staging); } +/* + * housekeeping_update - change housekeeping.cpumasks[type] and propagate the + * change. + */ +static int housekeeping_update(enum hk_type type, const struct cpumask *update) +{ + struct { + struct cpumask changed; + struct cpumask enable; + struct cpumask disable; + } *masks; + + masks = kmalloc(sizeof(*masks), GFP_KERNEL); + if (!masks) + return -ENOMEM; + + lockdep_assert_cpus_held(); + cpumask_xor(&masks->changed, housekeeping_cpumask(type), update); + cpumask_and(&masks->enable, &masks->changed, update); + cpumask_andnot(&masks->disable, &masks->changed, update); + cpumask_copy(housekeeping.cpumasks[type], update); + WRITE_ONCE(housekeeping.flags, housekeeping.flags | BIT(type)); + if (!static_branch_unlikely(&housekeeping_overridden)) + static_key_enable_cpuslocked(&housekeeping_overridden.key); + + /* Add here code to update dependent subsystems with + * changes of the housekeeping masks. + */ + + kfree(masks); + + return 0; +} + static int __init housekeeping_setup(char *str, unsigned long flags) { cpumask_var_t non_housekeeping_mask, housekeeping_staging; @@ -330,10 +364,12 @@ int housekeeping_exlude_isolcpus(const struct cpumask *isolcpus, unsigned long f /* * Reset housekeeping to bootup default */ + + for_each_clear_bit(type, &boot_hk_flags, HK_TYPE_MAX) + housekeeping_update(type, cpu_possible_mask); for_each_set_bit(type, &boot_hk_flags, HK_TYPE_MAX) - cpumask_copy(housekeeping.cpumasks[type], boot_hk_cpumask); + housekeeping_update(type, boot_hk_cpumask); - WRITE_ONCE(housekeeping.flags, boot_hk_flags); if (!boot_hk_flags && static_key_enabled(&housekeeping_overridden)) static_key_disable_cpuslocked(&housekeeping_overridden.key); return 0; @@ -358,9 +394,8 @@ int housekeeping_exlude_isolcpus(const struct cpumask *isolcpus, unsigned long f cpumask_andnot(tmp_mask, src_mask, isolcpus); if (!cpumask_intersects(tmp_mask, cpu_online_mask)) return -EINVAL; /* Invalid isolated CPUs */ - cpumask_copy(housekeeping.cpumasks[type], tmp_mask); + housekeeping_update(type, tmp_mask); } - WRITE_ONCE(housekeeping.flags, boot_hk_flags | flags); excluded = true; if (!static_key_enabled(&housekeeping_overridden)) static_key_enable_cpuslocked(&housekeeping_overridden.key); -- 2.47.0
