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Subject[tip:x86/boot] x86/smpboot: Remove APIC.wait_for_init_deassert and atomic init_deasserted
Commit-ID:  656bba306827a44ed73b3f93f75bb3147de17fae
Gitweb: http://git.kernel.org/tip/656bba306827a44ed73b3f93f75bb3147de17fae
Author: Len Brown <len.brown@intel.com>
AuthorDate: Sun, 16 Aug 2015 11:45:48 -0400
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 17 Aug 2015 10:42:28 +0200

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>
---
arch/x86/include/asm/apic.h | 2 --
arch/x86/kernel/apic/apic_flat_64.c | 2 --
arch/x86/kernel/apic/apic_noop.c | 1 -
arch/x86/kernel/apic/apic_numachip.c | 2 --
arch/x86/kernel/apic/bigsmp_32.c | 1 -
arch/x86/kernel/apic/probe_32.c | 1 -
arch/x86/kernel/apic/x2apic_cluster.c | 1 -
arch/x86/kernel/apic/x2apic_phys.c | 1 -
arch/x86/kernel/apic/x2apic_uv_x.c | 2 --
arch/x86/kernel/smpboot.c | 16 +++-------------
10 files changed, 3 insertions(+), 26 deletions(-)

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index c839363..ebf6d5e 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 de918c4..f92ab36 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 b205cdb..0d96749 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 017149c..b548fd3 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 c4a8d63..971cf88 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 bda4886..7694ae6 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 ab3219b..1b6c1a4 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 3ffd925..662e915 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 c8d9295..4a13946 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 6740264..c15d007 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");

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