Commit c8b7fb09 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Peter Zijlstra
Browse files

x86/smpboot: Remove cpu_callin_mask 



Now that TSC synchronization is SMP function call based there is no reason
to wait for the AP to be set in smp_callin_mask. The control CPU waits for
the AP to set itself in the online mask anyway.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: default avatarMichael Kelley <mikelley@microsoft.com>
Tested-by: default avatarOleksandr 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/20230512205256.206394064@linutronix.de
parent 9d349d47

arch/x86/kernel/smpboot.c

+15 −59
Original line number Diff line number Diff line
@@ -104,7 +104,6 @@ EXPORT_PER_CPU_SYMBOL(cpu_info); 
/* All of these masks are initialized in setup_cpu_local_masks() */

static cpumask_var_t cpu_initialized_mask;

static cpumask_var_t cpu_callout_mask;

static cpumask_var_t cpu_callin_mask;

/* Representing CPUs for which sibling maps can be computed */

static cpumask_var_t cpu_sibling_setup_mask;
@@ -161,38 +160,30 @@ static inline void smpboot_restore_warm_reset_vector(void) 


}



/*

 * Report back to the Boot Processor during boot time or to the caller processor

 * during CPU online.

 */

static void smp_callin(void)

/* Run the next set of setup steps for the upcoming CPU */

static void ap_starting(void)

{

	int cpuid;



	/*

	 * If waken up by an INIT in an 82489DX configuration

	 * cpu_callout_mask guarantees we don't get here before

	 * an INIT_deassert IPI reaches our local APIC, so it is

	 * now safe to touch our local APIC.

	 */

	cpuid = smp_processor_id();

	int cpuid = smp_processor_id();



	/*

	 * the boot CPU has finished the init stage and is spinning

	 * on callin_map until we finish. We are free to set up this

	 * CPU, first the APIC. (this is probably redundant on most

	 * boards)

	 * If woken up by an INIT in an 82489DX configuration

	 * cpu_callout_mask guarantees the CPU does not reach this point

	 * before an INIT_deassert IPI reaches the local APIC, so it is now

	 * safe to touch the local APIC.

	 *

	 * Set up this CPU, first the APIC, which is probably redundant on

	 * most boards.

	 */

	apic_ap_setup();



	/* Save our processor parameters. */

	/* Save the processor parameters. */

	smp_store_cpu_info(cpuid);



	/*

	 * The topology information must be up to date before

	 * notify_cpu_starting().

	 */

	set_cpu_sibling_map(raw_smp_processor_id());

	set_cpu_sibling_map(cpuid);



	ap_init_aperfmperf();
@@ -205,11 +196,6 @@ static void smp_callin(void) 
	 * state CPUHP_ONLINE.

	 */

	notify_cpu_starting(cpuid);



	/*

	 * Allow the master to continue.

	 */

	cpumask_set_cpu(cpuid, cpu_callin_mask);

}



static void ap_calibrate_delay(void)
@@ -268,12 +254,7 @@ static void notrace start_secondary(void *unused) 
	rcu_cpu_starting(raw_smp_processor_id());

	x86_cpuinit.early_percpu_clock_init();



	/*

	 * Sync point with wait_cpu_callin(). The AP doesn't wait here

	 * but just sets the bit to let the controlling CPU (BSP) know that

	 * it's got this far.

	 */

	smp_callin();

	ap_starting();



	/* Check TSC synchronization with the control CPU. */

	check_tsc_sync_target();
@@ -1109,7 +1090,7 @@ static int wait_cpu_cpumask(unsigned int cpu, const struct cpumask *mask) 
 * and thus wait_for_master_cpu(), then set cpu_callout_mask to allow it

 * to proceed.  The AP will then proceed past setting its 'callin' bit

 * and end up waiting in check_tsc_sync_target() until we reach

 * do_wait_cpu_online() to tend to it.

 * wait_cpu_online() to tend to it.

 */

static int wait_cpu_initialized(unsigned int cpu)

{
@@ -1124,20 +1105,7 @@ static int wait_cpu_initialized(unsigned int cpu) 
}



/*

 * Bringup step three: Wait for the target AP to reach smp_callin().

 * The AP is not waiting for us here so we don't need to parallelise

 * this step. Not entirely clear why we care about this, since we just

 * proceed directly to TSC synchronization which is the next sync

 * point with the AP anyway.

 */

static void wait_cpu_callin(unsigned int cpu)

{

	while (!cpumask_test_cpu(cpu, cpu_callin_mask))

		schedule();

}



/*

 * Bringup step four: Wait for the target AP to reach set_cpu_online() in

 * Bringup step three: Wait for the target AP to reach set_cpu_online() in

 * start_secondary().

 */

static void wait_cpu_online(unsigned int cpu)
@@ -1166,14 +1134,6 @@ static int native_kick_ap(unsigned int cpu, struct task_struct *tidle) 
		return -EINVAL;

	}



	/*

	 * Already booted CPU?

	 */

	if (cpumask_test_cpu(cpu, cpu_callin_mask)) {

		pr_debug("do_boot_cpu %d Already started\n", cpu);

		return -ENOSYS;

	}



	/*

	 * Save current MTRR state in case it was changed since early boot

	 * (e.g. by the ACPI SMI) to initialize new CPUs with MTRRs in sync:
@@ -1211,7 +1171,6 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle) 
	if (ret)

		goto out;



	wait_cpu_callin(cpu);

	wait_cpu_online(cpu);



out:
@@ -1327,7 +1286,6 @@ void __init smp_prepare_cpus_common(void) 
	 * Setup boot CPU information

	 */

	smp_store_boot_cpu_info(); /* Final full version of the data */

	cpumask_copy(cpu_callin_mask, cpumask_of(0));

	mb();



	for_each_possible_cpu(i) {
@@ -1542,7 +1500,6 @@ __init void prefill_possible_map(void) 
void __init setup_cpu_local_masks(void)

{

	alloc_bootmem_cpumask_var(&cpu_initialized_mask);

	alloc_bootmem_cpumask_var(&cpu_callin_mask);

	alloc_bootmem_cpumask_var(&cpu_callout_mask);

	alloc_bootmem_cpumask_var(&cpu_sibling_setup_mask);

}
@@ -1606,7 +1563,6 @@ static void remove_cpu_from_maps(int cpu) 
{

	set_cpu_online(cpu, false);

	cpumask_clear_cpu(cpu, cpu_callout_mask);

	cpumask_clear_cpu(cpu, cpu_callin_mask);

	/* was set by cpu_init() */

	cpumask_clear_cpu(cpu, cpu_initialized_mask);

	numa_remove_cpu(cpu);