Hi Drew,
On 10/31/24 13:39, Andrew Jones wrote:
> on_cpumask should wait until the cpus in the mask, not including
> the calling cpu, are idle. Checking the weight against nr_cpus
> minus 1 only works when the mask is the same as the present mask.
>
> Fixes: d012cfd5d309 ("lib/on-cpus: Introduce on_cpumask and on_cpumask_async")
> Signed-off-by: Andrew Jones <andrew.jones@xxxxxxxxx>
looks good to me as well
Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
Eric
> ---
> lib/cpumask.h | 14 ++++++++++++++
> lib/on-cpus.c | 17 ++++++++---------
> 2 files changed, 22 insertions(+), 9 deletions(-)
>
> diff --git a/lib/cpumask.h b/lib/cpumask.h
> index e1e92aacd1f1..37d360786573 100644
> --- a/lib/cpumask.h
> +++ b/lib/cpumask.h
> @@ -58,6 +58,20 @@ static inline void cpumask_clear(cpumask_t *mask)
> memset(mask, 0, sizeof(*mask));
> }
>
> +/* true if src1 is a subset of src2 */
> +static inline bool cpumask_subset(const struct cpumask *src1, const struct cpumask *src2)
> +{
> + unsigned long lastmask = BIT_MASK(nr_cpus) - 1;
> + int i;
> +
> + for (i = 0; i < BIT_WORD(nr_cpus); ++i) {
> + if (cpumask_bits(src1)[i] & ~cpumask_bits(src2)[i])
> + return false;
> + }
> +
> + return !lastmask || !((cpumask_bits(src1)[i] & ~cpumask_bits(src2)[i]) & lastmask);
> +}
> +
> static inline bool cpumask_empty(const cpumask_t *mask)
> {
> unsigned long lastmask = BIT_MASK(nr_cpus) - 1;
> diff --git a/lib/on-cpus.c b/lib/on-cpus.c
> index 356f284be61b..889b6bc8a186 100644
> --- a/lib/on-cpus.c
> +++ b/lib/on-cpus.c
> @@ -127,24 +127,23 @@ void on_cpumask_async(const cpumask_t *mask, void (*func)(void *data), void *dat
> void on_cpumask(const cpumask_t *mask, void (*func)(void *data), void *data)
> {
> int cpu, me = smp_processor_id();
> + cpumask_t tmp;
>
> - for_each_cpu(cpu, mask) {
> - if (cpu == me)
> - continue;
> + cpumask_copy(&tmp, mask);
> + cpumask_clear_cpu(me, &tmp);
> +
> + for_each_cpu(cpu, &tmp)
> on_cpu_async(cpu, func, data);
> - }
> if (cpumask_test_cpu(me, mask))
> func(data);
>
> - for_each_cpu(cpu, mask) {
> - if (cpu == me)
> - continue;
> + for_each_cpu(cpu, &tmp) {
> cpumask_set_cpu(me, &on_cpu_info[cpu].waiters);
> deadlock_check(me, cpu);
> }
> - while (cpumask_weight(&cpu_idle_mask) < nr_cpus - 1)
> + while (!cpumask_subset(&tmp, &cpu_idle_mask))
> smp_wait_for_event();
> - for_each_cpu(cpu, mask)
> + for_each_cpu(cpu, &tmp)
> cpumask_clear_cpu(me, &on_cpu_info[cpu].waiters);
> smp_rmb(); /* pairs with the smp_wmb() in do_idle() */
> }
