x86/smpboot: Remove APIC.wait_for_init_deassert and atomic init_deasserted

Both the per-APIC flag ".wait_for_init_deassert",
and the global atomic_t "init_deasserted"
are dead code -- remove them.

For all APIC types, "wait_for_master()"
prevents an AP from proceeding until the BSP has set
cpu_callout_mask, making "init_deasserted" {unnecessary}:

	BSP: <de-assert INIT>
	...
	BSP: {set init_deasserted}
	AP: wait_for_master()
		set cpu_initialized_mask
		wait for cpu_callout_mask
	BSP: test cpu_initialized_mask
	BSP: set cpu_callout_mask
	AP: test cpu_callout_mask
	AP: {wait for init_deasserted}
	...
	AP: <touch APIC>

Deleting the {dead code} above is necessary to enable
some parallelism in a future patch.

Signed-off-by: Len Brown <len.brown@intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Jan H. Schönherr <jschoenh@amazon.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Zhu Guihua <zhugh.fnst@cn.fujitsu.com>
Link: http://lkml.kernel.org/r/de4b3a9bab894735e285870b5296da25ee6a8a5a.1439739165.git.len.brown@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

10 files changed, 3 insertions, 26 deletions

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index c8393634ca0c..ebf6d5e5668c 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -313,7 +313,6 @@ struct apic {
         /* wakeup_secondary_cpu */
         int (*wakeup_secondary_cpu)(int apicid, unsigned long start_eip);
 
-        bool wait_for_init_deassert;
         void (*inquire_remote_apic)(int apicid);
 
         /* apic ops */
@@ -378,7 +377,6 @@ extern struct apic *__apicdrivers[], *__apicdrivers_end[];
  * APIC functionality to boot other CPUs - only used on SMP:
  */
 #ifdef CONFIG_SMP
-extern atomic_t init_deasserted;
 extern int wakeup_secondary_cpu_via_nmi(int apicid, unsigned long start_eip);
 #endif
 
diff --git a/arch/x86/kernel/apic/apic_flat_64.c b/arch/x86/kernel/apic/apic_flat_64.c
index de918c410eae..f92ab36979a2 100644
--- a/arch/x86/kernel/apic/apic_flat_64.c
+++ b/arch/x86/kernel/apic/apic_flat_64.c
@@ -191,7 +191,6 @@ static struct apic apic_flat =  {
         .send_IPI_all                   = flat_send_IPI_all,
         .send_IPI_self                  = apic_send_IPI_self,
 
-        .wait_for_init_deassert         = false,
         .inquire_remote_apic            = default_inquire_remote_apic,
 
         .read                           = native_apic_mem_read,
@@ -299,7 +298,6 @@ static struct apic apic_physflat =  {
         .send_IPI_all                   = physflat_send_IPI_all,
         .send_IPI_self                  = apic_send_IPI_self,
 
-        .wait_for_init_deassert         = false,
         .inquire_remote_apic            = default_inquire_remote_apic,
 
         .read                           = native_apic_mem_read,
diff --git a/arch/x86/kernel/apic/apic_noop.c b/arch/x86/kernel/apic/apic_noop.c
index b205cdbdbe6a..0d96749cfcac 100644
--- a/arch/x86/kernel/apic/apic_noop.c
+++ b/arch/x86/kernel/apic/apic_noop.c
@@ -152,7 +152,6 @@ struct apic apic_noop = {
 
         .wakeup_secondary_cpu           = noop_wakeup_secondary_cpu,
 
-        .wait_for_init_deassert         = false,
         .inquire_remote_apic            = NULL,
 
         .read                           = noop_apic_read,
diff --git a/arch/x86/kernel/apic/apic_numachip.c b/arch/x86/kernel/apic/apic_numachip.c
index 017149cded07..b548fd3b764b 100644
--- a/arch/x86/kernel/apic/apic_numachip.c
+++ b/arch/x86/kernel/apic/apic_numachip.c
@@ -92,7 +92,6 @@ static int numachip_wakeup_secondary(int phys_apicid, unsigned long start_rip)
 
         write_lcsr(CSR_G3_EXT_IRQ_GEN, int_gen.v);
 
-        atomic_set(&init_deasserted, 1);
         return 0;
 }
 
@@ -235,7 +234,6 @@ static const struct apic apic_numachip __refconst = {
         .send_IPI_self                  = numachip_send_IPI_self,
 
         .wakeup_secondary_cpu           = numachip_wakeup_secondary,
-        .wait_for_init_deassert         = false,
         .inquire_remote_apic            = NULL, /* REMRD not supported */
 
         .read                           = native_apic_mem_read,
diff --git a/arch/x86/kernel/apic/bigsmp_32.c b/arch/x86/kernel/apic/bigsmp_32.c
index c4a8d63f8220..971cf8875939 100644
--- a/arch/x86/kernel/apic/bigsmp_32.c
+++ b/arch/x86/kernel/apic/bigsmp_32.c
@@ -186,7 +186,6 @@ static struct apic apic_bigsmp = {
         .send_IPI_all                   = bigsmp_send_IPI_all,
         .send_IPI_self                  = default_send_IPI_self,
 
-        .wait_for_init_deassert         = true,
         .inquire_remote_apic            = default_inquire_remote_apic,
 
         .read                           = native_apic_mem_read,
diff --git a/arch/x86/kernel/apic/probe_32.c b/arch/x86/kernel/apic/probe_32.c
index bda488680dbc..7694ae6c1199 100644
--- a/arch/x86/kernel/apic/probe_32.c
+++ b/arch/x86/kernel/apic/probe_32.c
@@ -111,7 +111,6 @@ static struct apic apic_default = {
         .send_IPI_all                   = default_send_IPI_all,
         .send_IPI_self                  = default_send_IPI_self,
 
-        .wait_for_init_deassert         = true,
         .inquire_remote_apic            = default_inquire_remote_apic,
 
         .read                           = native_apic_mem_read,
diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c
index ab3219b3fbda..1b6c1a4526a5 100644
--- a/arch/x86/kernel/apic/x2apic_cluster.c
+++ b/arch/x86/kernel/apic/x2apic_cluster.c
@@ -272,7 +272,6 @@ static struct apic apic_x2apic_cluster = {
         .send_IPI_all                   = x2apic_send_IPI_all,
         .send_IPI_self                  = x2apic_send_IPI_self,
 
-        .wait_for_init_deassert         = false,
         .inquire_remote_apic            = NULL,
 
         .read                           = native_apic_msr_read,
diff --git a/arch/x86/kernel/apic/x2apic_phys.c b/arch/x86/kernel/apic/x2apic_phys.c
index 3ffd925655e0..662e9150ea6f 100644
--- a/arch/x86/kernel/apic/x2apic_phys.c
+++ b/arch/x86/kernel/apic/x2apic_phys.c
@@ -128,7 +128,6 @@ static struct apic apic_x2apic_phys = {
         .send_IPI_all                   = x2apic_send_IPI_all,
         .send_IPI_self                  = x2apic_send_IPI_self,
 
-        .wait_for_init_deassert         = false,
         .inquire_remote_apic            = NULL,
 
         .read                           = native_apic_msr_read,
diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c b/arch/x86/kernel/apic/x2apic_uv_x.c
index c8d92950bc04..4a139465f1d4 100644
--- a/arch/x86/kernel/apic/x2apic_uv_x.c
+++ b/arch/x86/kernel/apic/x2apic_uv_x.c
@@ -248,7 +248,6 @@ static int uv_wakeup_secondary(int phys_apicid, unsigned long start_rip)
             APIC_DM_STARTUP;
         uv_write_global_mmr64(pnode, UVH_IPI_INT, val);
 
-        atomic_set(&init_deasserted, 1);
         return 0;
 }
 
@@ -414,7 +413,6 @@ static struct apic __refdata apic_x2apic_uv_x = {
         .send_IPI_self                  = uv_send_IPI_self,
 
         .wakeup_secondary_cpu           = uv_wakeup_secondary,
-        .wait_for_init_deassert         = false,
         .inquire_remote_apic            = NULL,
 
         .read                           = native_apic_msr_read,
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 674026455fee..c15d0073c829 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -97,8 +97,6 @@ DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_llc_shared_map);
 DEFINE_PER_CPU_READ_MOSTLY(struct cpuinfo_x86, cpu_info);
 EXPORT_PER_CPU_SYMBOL(cpu_info);
 
-atomic_t init_deasserted;
-
 static inline void smpboot_setup_warm_reset_vector(unsigned long start_eip)
 {
         unsigned long flags;
@@ -146,16 +144,11 @@ static void smp_callin(void)
 
         /*
          * If waken up by an INIT in an 82489DX configuration
-         * we may get here before an INIT-deassert IPI reaches
-         * our local APIC.  We have to wait for the IPI or we'll
-         * lock up on an APIC access.
-         *
-         * Since CPU0 is not wakened up by INIT, it doesn't wait for the IPI.
+         * 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();
-        if (apic->wait_for_init_deassert && cpuid)
-                while (!atomic_read(&init_deasserted))
-                        cpu_relax();
 
         /*
          * (This works even if the APIC is not enabled.)
@@ -620,7 +613,6 @@ wakeup_secondary_cpu_via_init(int phys_apicid, unsigned long start_eip)
         send_status = safe_apic_wait_icr_idle();
 
         mb();
-        atomic_set(&init_deasserted, 1);
 
         /*
          * Should we send STARTUP IPIs ?
@@ -861,8 +853,6 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
          * the targeted processor.
          */
 
-        atomic_set(&init_deasserted, 0);
-
         if (get_uv_system_type() != UV_NON_UNIQUE_APIC) {
 
                 pr_debug("Setting warm reset code and vector.\n");