[tip: smp/core] x86/smpboot: Remove cpu_callin_mask
From: tip-bot2 for Thomas Gleixner
Date: Tue May 16 2023 - 05:11:58 EST
The following commit has been merged into the smp/core branch of tip:
Commit-ID: c8b7fb09d1bcfa61d4211f61542e1291e7b4cbad
Gitweb: https://git.kernel.org/tip/c8b7fb09d1bcfa61d4211f61542e1291e7b4cbad
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Fri, 12 May 2023 23:07:19 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Mon, 15 May 2023 13:44:53 +02:00
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: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Tested-by: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx>
Tested-by: Helge Deller <deller@xxxxxx> # parisc
Tested-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx> # Steam Deck
Link: https://lore.kernel.org/r/20230512205256.206394064@xxxxxxxxxxxxx
---
arch/x86/kernel/smpboot.c | 74 +++++++-------------------------------
1 file changed, 15 insertions(+), 59 deletions(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index b2f44a8..3f731be 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -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)
@@ -1167,14 +1135,6 @@ static int native_kick_ap(unsigned int cpu, struct task_struct *tidle)
}
/*
- * 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);