On 25/05/2017 12:28, Andrew Jones wrote:
> A common pattern is
> - run a function on all cpus
> - signal each cpu's completion with a cpumask
> - halt the secondaries when they're complete
> - have the primary wait on the cpumask for all to complete
>
> smp_run is a wrapper for that pattern. Also, we were allowing
> secondaries to go off in the weeds if they returned from their
> secondary entry function, which can be difficult to debug. A
> nice side-effect of adding this wrapper is we don't do that
> anymore, and can even know when a secondary has halted with the
> new cpu_halted_mask.
Would it make sense to just call main() this way?
Paolo
> Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
> ---
> arm/cstart.S | 3 ++-
> arm/cstart64.S | 3 ++-
> lib/arm/asm/smp.h | 2 ++
> lib/arm/smp.c | 26 ++++++++++++++++++++++++++
> 4 files changed, 32 insertions(+), 2 deletions(-)
>
> diff --git a/arm/cstart.S b/arm/cstart.S
> index 12461d104dad..b3176b274933 100644
> --- a/arm/cstart.S
> +++ b/arm/cstart.S
> @@ -118,7 +118,8 @@ secondary_entry:
> bl secondary_cinit
>
> /* r0 is now the entry function, run it */
> - mov pc, r0
> + blx r0
> + b secondary_halt
>
> .globl halt
> halt:
> diff --git a/arm/cstart64.S b/arm/cstart64.S
> index 7738babc4109..30f732f1e99b 100644
> --- a/arm/cstart64.S
> +++ b/arm/cstart64.S
> @@ -79,7 +79,8 @@ secondary_entry:
> bl secondary_cinit
>
> /* x0 is now the entry function, run it */
> - br x0
> + blr x0
> + b secondary_halt
>
> .globl halt
> halt:
> diff --git a/lib/arm/asm/smp.h b/lib/arm/asm/smp.h
> index 4cb86b6ce342..1d1cd7a29991 100644
> --- a/lib/arm/asm/smp.h
> +++ b/lib/arm/asm/smp.h
> @@ -14,6 +14,7 @@ extern void halt(void);
>
> extern cpumask_t cpu_present_mask;
> extern cpumask_t cpu_online_mask;
> +extern cpumask_t cpu_halted_mask;
> #define cpu_present(cpu) cpumask_test_cpu(cpu, &cpu_present_mask)
> #define cpu_online(cpu) cpumask_test_cpu(cpu, &cpu_online_mask)
> #define for_each_present_cpu(cpu) for_each_cpu(cpu, &cpu_present_mask)
> @@ -45,5 +46,6 @@ struct secondary_data {
> extern struct secondary_data secondary_data;
>
> extern void smp_boot_secondary(int cpu, secondary_entry_fn entry);
> +extern void smp_run(void (*func)(void));
>
> #endif /* _ASMARM_SMP_H_ */
> diff --git a/lib/arm/smp.c b/lib/arm/smp.c
> index bbaf9e60e950..8528aa454108 100644
> --- a/lib/arm/smp.c
> +++ b/lib/arm/smp.c
> @@ -15,6 +15,7 @@
>
> cpumask_t cpu_present_mask;
> cpumask_t cpu_online_mask;
> +cpumask_t cpu_halted_mask;
> struct secondary_data secondary_data;
>
> secondary_entry_fn secondary_cinit(void)
> @@ -53,3 +54,28 @@ void smp_boot_secondary(int cpu, secondary_entry_fn entry)
> while (!cpu_online(cpu))
> wfe();
> }
> +
> +void secondary_halt(void)
> +{
> + struct thread_info *ti = current_thread_info();
> +
> + cpumask_set_cpu(ti->cpu, &cpu_halted_mask);
> + halt();
> +}
> +
> +void smp_run(void (*func)(void))
> +{
> + int cpu;
> +
> + for_each_present_cpu(cpu) {
> + if (cpu == 0)
> + continue;
> + smp_boot_secondary(cpu, func);
> + }
> + func();
> +
> + cpumask_set_cpu(0, &cpu_halted_mask);
> + while (!cpumask_full(&cpu_halted_mask))
> + cpu_relax();
> + cpumask_clear_cpu(0, &cpu_halted_mask);
> +}
>
