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cpu/hotplug: Rework sparse_irq locking in bringup_cpu() 

There is no harm to hold sparse_irq lock until the upcoming CPU completes
in cpuhp_online_idle(). This allows to remove cpu_online() synchronization
from architecture code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> # Steam Deck
Link: https://lore.kernel.org/r/20230512205256.263722880@linutronix.de
This commit is contained in:
Thomas Gleixner 2023-05-12 23:07:21 +02:00 committed by Peter Zijlstra
parent c8b7fb09d1
commit 22b612e2d5
1 changed files with 24 additions and 10 deletions
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34
kernel/cpu.c
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@ -558,7 +558,7 @@ static int cpuhp_kick_ap(int cpu, struct cpuhp_cpu_state *st,
return ret;
}
static int bringup_wait_for_ap(unsigned int cpu)
static int bringup_wait_for_ap_online(unsigned int cpu)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
@ -579,15 +579,12 @@ static int bringup_wait_for_ap(unsigned int cpu)
*/
if (!cpu_smt_allowed(cpu))
return -ECANCELED;
if (st->target <= CPUHP_AP_ONLINE_IDLE)
return 0;
return cpuhp_kick_ap(cpu, st, st->target);
return 0;
}
static int bringup_cpu(unsigned int cpu)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
struct task_struct *idle = idle_thread_get(cpu);
int ret;
@ -600,16 +597,33 @@ static int bringup_cpu(unsigned int cpu)
/*
* Some architectures have to walk the irq descriptors to
* setup the vector space for the cpu which comes online.
* Prevent irq alloc/free across the bringup.
*
* Prevent irq alloc/free across the bringup by acquiring the
* sparse irq lock. Hold it until the upcoming CPU completes the
* startup in cpuhp_online_idle() which allows to avoid
* intermediate synchronization points in the architecture code.
*/
irq_lock_sparse();
/* Arch-specific enabling code. */
ret = __cpu_up(cpu, idle);
irq_unlock_sparse();
if (ret)
return ret;
return bringup_wait_for_ap(cpu);
goto out_unlock;
ret = bringup_wait_for_ap_online(cpu);
if (ret)
goto out_unlock;
irq_unlock_sparse();
if (st->target <= CPUHP_AP_ONLINE_IDLE)
return 0;
return cpuhp_kick_ap(cpu, st, st->target);
out_unlock:
irq_unlock_sparse();
return ret;
}
static int finish_cpu(unsigned int cpu)