mirror of
https://github.com/brain-hackers/linux-brain.git
synced 2024-06-09 23:36:23 +09:00
3bd3706251
In commit:
4b53a3412d ("sched/core: Remove the tsk_nr_cpus_allowed() wrapper")
the tsk_nr_cpus_allowed() wrapper was removed. There was not
much difference in !RT but in RT we used this to implement
migrate_disable(). Within a migrate_disable() section the CPU mask is
restricted to single CPU while the "normal" CPU mask remains untouched.
As an alternative implementation Ingo suggested to use:
struct task_struct {
const cpumask_t *cpus_ptr;
cpumask_t cpus_mask;
};
with
t->cpus_ptr = &t->cpus_mask;
In -RT we then can switch the cpus_ptr to:
t->cpus_ptr = &cpumask_of(task_cpu(p));
in a migration disabled region. The rules are simple:
- Code that 'uses' ->cpus_allowed would use the pointer.
- Code that 'modifies' ->cpus_allowed would use the direct mask.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190423142636.14347-1-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
68 lines
1.5 KiB
C
68 lines
1.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
|
* lib/smp_processor_id.c
|
|
*
|
|
* DEBUG_PREEMPT variant of smp_processor_id().
|
|
*/
|
|
#include <linux/export.h>
|
|
#include <linux/kprobes.h>
|
|
#include <linux/sched.h>
|
|
|
|
notrace static nokprobe_inline
|
|
unsigned int check_preemption_disabled(const char *what1, const char *what2)
|
|
{
|
|
int this_cpu = raw_smp_processor_id();
|
|
|
|
if (likely(preempt_count()))
|
|
goto out;
|
|
|
|
if (irqs_disabled())
|
|
goto out;
|
|
|
|
/*
|
|
* Kernel threads bound to a single CPU can safely use
|
|
* smp_processor_id():
|
|
*/
|
|
if (cpumask_equal(current->cpus_ptr, cpumask_of(this_cpu)))
|
|
goto out;
|
|
|
|
/*
|
|
* It is valid to assume CPU-locality during early bootup:
|
|
*/
|
|
if (system_state < SYSTEM_SCHEDULING)
|
|
goto out;
|
|
|
|
/*
|
|
* Avoid recursion:
|
|
*/
|
|
preempt_disable_notrace();
|
|
|
|
if (!printk_ratelimit())
|
|
goto out_enable;
|
|
|
|
printk(KERN_ERR "BUG: using %s%s() in preemptible [%08x] code: %s/%d\n",
|
|
what1, what2, preempt_count() - 1, current->comm, current->pid);
|
|
|
|
printk("caller is %pS\n", __builtin_return_address(0));
|
|
dump_stack();
|
|
|
|
out_enable:
|
|
preempt_enable_no_resched_notrace();
|
|
out:
|
|
return this_cpu;
|
|
}
|
|
|
|
notrace unsigned int debug_smp_processor_id(void)
|
|
{
|
|
return check_preemption_disabled("smp_processor_id", "");
|
|
}
|
|
EXPORT_SYMBOL(debug_smp_processor_id);
|
|
NOKPROBE_SYMBOL(debug_smp_processor_id);
|
|
|
|
notrace void __this_cpu_preempt_check(const char *op)
|
|
{
|
|
check_preemption_disabled("__this_cpu_", op);
|
|
}
|
|
EXPORT_SYMBOL(__this_cpu_preempt_check);
|
|
NOKPROBE_SYMBOL(__this_cpu_preempt_check);
|