Hi Dawei,
> About this case, it's kinda tricky for:
> - dr_cpu_data() returns void, so alloc_cpumask_var() is no go.
>
> - No idea of the calling context of dr_cpu_data(). IIUC,
> dr_cpu_data()
> ->dr_cpu_configure()
> ->kzalloc(resp_len, GFP_KERNEL)
> So I guess it's in process context?
> If consumption above is OK, a simple but _ugly_ solution could be:
>
> diff --git a/arch/sparc/kernel/ds.c b/arch/sparc/kernel/ds.c
> index ffdc15588ac2..c9e4ebdccf49 100644
> --- a/arch/sparc/kernel/ds.c
> +++ b/arch/sparc/kernel/ds.c
> @@ -634,7 +634,8 @@ static void dr_cpu_data(struct ds_info *dp, struct ds_cap_state *cp, void *buf,
> struct dr_cpu_tag *tag = (struct dr_cpu_tag *) (data + 1);
> u32 *cpu_list = (u32 *) (tag + 1);
> u64 req_num = tag->req_num;
> - cpumask_t mask;
> + static DEFINE_MUTEX(mask_lock);
> + static cpumask_t mask;
> unsigned int i;
> int err;
>
> @@ -651,6 +652,8 @@ static void dr_cpu_data(struct ds_info *dp, struct ds_cap_state *cp, void *buf,
>
> purge_dups(cpu_list, tag->num_records);
>
> + mutex_lock(&mask_lock);
> +
> cpumask_clear(&mask);
> for (i = 0; i < tag->num_records; i++) {
> if (cpu_list[i] == CPU_SENTINEL)
> @@ -665,6 +668,8 @@ static void dr_cpu_data(struct ds_info *dp, struct ds_cap_state *cp, void *buf,
> else
> err = dr_cpu_unconfigure(dp, cp, req_num, &mask);
>
> + mutex_unlock(&mask_lock);
> +
> if (err)
> dr_cpu_send_error(dp, cp, data);
> }
>
> How does it sound to you?
This introduces too much complexity to solve a potential stack issue.
If an improvement is required, then we need a simpler solution.
>
> > kernel/leon_kernel.c: cpumask_t mask;
>
> It's in irqchip::irq_set_affinity(), which is in atomic context(raw spinlock(s) held),
> so dynamic allocation is not a good idea.
>
> My proposal(*untested*) is somewhat complicated for it introduces a new helper.
>
> diff --git a/arch/sparc/kernel/leon_kernel.c b/arch/sparc/kernel/leon_kernel.c
> index 4c61da491fee..6eced7acb8bc 100644
> --- a/arch/sparc/kernel/leon_kernel.c
> +++ b/arch/sparc/kernel/leon_kernel.c
> @@ -104,15 +104,25 @@ unsigned long leon_get_irqmask(unsigned int irq)
> }
>
> #ifdef CONFIG_SMP
> +
> +static bool cpumask_include(const struct cpumask *srcp1, const struct cpumask *srcp2)
> +{
> + unsigned int cpu;
> +
> + for_each_cpu(cpu, srcp2) {
> + if (!cpumask_test_cpu(cpu, srcp1))
> + return false;
> + }
> +
> + return true;
> +}
> +
> static int irq_choose_cpu(const struct cpumask *affinity)
> {
> - cpumask_t mask;
> + unsigned int cpu = cpumask_first_and(affinity, cpu_online_mask);
>
> - cpumask_and(&mask, cpu_online_mask, affinity);
> - if (cpumask_equal(&mask, cpu_online_mask) || cpumask_empty(&mask))
> - return boot_cpu_id;
> - else
> - return cpumask_first(&mask);
> + return cpumask_include(affinity, cpu_online_mask) || cpu >= nr_cpu_ids ?
> + boot_cpu_id : cpu;
> }
I think something like the following should do the trick.
if (cpumask_equal(affinity, cpu_online_mask))
return boot_cpu_id;
cpuid = cpumask_first_and(affinity, cpu_online_mask);
if (cpuid < nr_cpu_ids)
return cpuid;
else
return boot_cpu_id;
If the passed affinity equals the online cpu's, then use the boot cpu.
Else, use the first online cpu in the affinity mask.
If none found use the boot cpu.
> #else
> #define irq_choose_cpu(affinity) boot_cpu_id
>
> Is it OK?
>
> [cc Yury for bitmap API]
>
> > kernel/leon_smp.c:static void leon_cross_call(void *func, cpumask_t mask, unsigned long arg1,
> > kernel/sun4d_smp.c:static void sun4d_cross_call(void *func, cpumask_t mask, unsigned long arg1,
Looks simple, just pass a pointer and not by value.
>
> Actually I am awared of existence of (at least some of) them, but so far I
> have not found a _proper_ way of dealing with them(especially for case of
> ds.c).
>
> Please lemme dig into it.
Looks forward to next iteration.
Sam
