On Mon, 2011-01-17 at 12:31 +0100, Peter Zijlstra wrote:
> On Mon, 2011-01-17 at 11:26 +0000, Russell King - ARM Linux wrote:
> > Maybe remove the comment "everything is done on the interrupt return path"
> > as with this function call, that is no longer the case.
(Removed am33, m32r-ka, m32r, arm-kernel lists because they kept sending
bounces)
---
Subject: sched: provide scheduler_ipi() callback in response to
smp_send_reschedule()
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Mon, 17 Jan 2011 12:07:13 +0100
For future rework of try_to_wake_up() we'd like to push part of that
onto the CPU the task is actually going to run on, in order to do so we
need a generic callback from the existing scheduler IPI.
This patch introduces such a generic callback: scheduler_ipi() and
implements it as a NOP.
I visited existing smp_send_reschedule() implementations and tried to
add a call to scheduler_ipi() in their handler part, but esp. for MIPS
I'm not quite sure I actually got all of them.
Also, while reading through all this, I noticed the blackfin SMP code
looks to be broken, it simply discards any IPI when low on memory.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
LKML-Reference: <new-submission>
---
arch/alpha/kernel/smp.c | 3 +--
arch/arm/kernel/smp.c | 5 +----
arch/blackfin/mach-common/smp.c | 5 ++---
arch/cris/arch-v32/kernel/smp.c | 13 ++++++++-----
arch/ia64/kernel/irq_ia64.c | 2 ++
arch/ia64/xen/irq_xen.c | 10 +++++++++-
arch/m32r/kernel/smp.c | 4 +---
arch/mips/kernel/smtc.c | 2 +-
arch/mips/sibyte/bcm1480/smp.c | 7 +++----
arch/mips/sibyte/sb1250/smp.c | 7 +++----
arch/mn10300/kernel/smp.c | 5 +----
arch/parisc/kernel/smp.c | 5 +----
arch/powerpc/kernel/smp.c | 2 +-
arch/s390/kernel/smp.c | 6 +++---
arch/sh/kernel/smp.c | 2 ++
arch/sparc/kernel/smp_32.c | 2 +-
arch/sparc/kernel/smp_64.c | 1 +
arch/tile/kernel/smp.c | 6 +-----
arch/um/kernel/smp.c | 2 +-
arch/x86/kernel/smp.c | 5 ++---
arch/x86/xen/smp.c | 5 ++---
include/linux/sched.h | 1 +
22 files changed, 48 insertions(+), 52 deletions(-)
Index: linux-2.6/arch/alpha/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/alpha/kernel/smp.c
+++ linux-2.6/arch/alpha/kernel/smp.c
@@ -585,8 +585,7 @@ handle_ipi(struct pt_regs *regs)
switch (which) {
case IPI_RESCHEDULE:
- /* Reschedule callback. Everything to be done
- is done by the interrupt return path. */
+ scheduler_ipi();
break;
case IPI_CALL_FUNC:
Index: linux-2.6/arch/arm/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/arm/kernel/smp.c
+++ linux-2.6/arch/arm/kernel/smp.c
@@ -575,10 +575,7 @@ asmlinkage void __exception do_IPI(struc
break;
case IPI_RESCHEDULE:
- /*
- * nothing more to do - eveything is
- * done on the interrupt return path
- */
+ scheduler_ipi();
break;
case IPI_CALL_FUNC:
Index: linux-2.6/arch/blackfin/mach-common/smp.c
===================================================================
--- linux-2.6.orig/arch/blackfin/mach-common/smp.c
+++ linux-2.6/arch/blackfin/mach-common/smp.c
@@ -154,8 +154,7 @@ static irqreturn_t ipi_handler(int irq,
list_del(&msg->list);
switch (msg->type) {
case BFIN_IPI_RESCHEDULE:
- /* That's the easiest one; leave it to
- * return_from_int. */
+ scheduler_ipi();
kfree(msg);
break;
case BFIN_IPI_CALL_FUNC:
@@ -301,7 +300,7 @@ void smp_send_reschedule(int cpu)
msg = kzalloc(sizeof(*msg), GFP_ATOMIC);
if (!msg)
- return;
+ return; /* XXX unreliable needs fixing ! */
INIT_LIST_HEAD(&msg->list);
msg->type = BFIN_IPI_RESCHEDULE;
Index: linux-2.6/arch/cris/arch-v32/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/cris/arch-v32/kernel/smp.c
+++ linux-2.6/arch/cris/arch-v32/kernel/smp.c
@@ -340,15 +340,18 @@ irqreturn_t crisv32_ipi_interrupt(int ir
ipi = REG_RD(intr_vect, irq_regs[smp_processor_id()], rw_ipi);
+ if (ipi.vector & IPI_SCHEDULE) {
+ scheduler_ipi();
+ }
if (ipi.vector & IPI_CALL) {
- func(info);
+ func(info);
}
if (ipi.vector & IPI_FLUSH_TLB) {
- if (flush_mm == FLUSH_ALL)
- __flush_tlb_all();
- else if (flush_vma == FLUSH_ALL)
+ if (flush_mm == FLUSH_ALL)
+ __flush_tlb_all();
+ else if (flush_vma == FLUSH_ALL)
__flush_tlb_mm(flush_mm);
- else
+ else
__flush_tlb_page(flush_vma, flush_addr);
}
Index: linux-2.6/arch/ia64/kernel/irq_ia64.c
===================================================================
--- linux-2.6.orig/arch/ia64/kernel/irq_ia64.c
+++ linux-2.6/arch/ia64/kernel/irq_ia64.c
@@ -31,6 +31,7 @@
#include <linux/irq.h>
#include <linux/ratelimit.h>
#include <linux/acpi.h>
+#include <linux/sched.h>
#include <asm/delay.h>
#include <asm/intrinsics.h>
@@ -496,6 +497,7 @@ ia64_handle_irq (ia64_vector vector, str
smp_local_flush_tlb();
kstat_incr_irqs_this_cpu(irq, desc);
} else if (unlikely(IS_RESCHEDULE(vector))) {
+ scheduler_ipi();
kstat_incr_irqs_this_cpu(irq, desc);
} else {
ia64_setreg(_IA64_REG_CR_TPR, vector);
Index: linux-2.6/arch/ia64/xen/irq_xen.c
===================================================================
--- linux-2.6.orig/arch/ia64/xen/irq_xen.c
+++ linux-2.6/arch/ia64/xen/irq_xen.c
@@ -92,6 +92,8 @@ static unsigned short saved_irq_cnt;
static int xen_slab_ready;
#ifdef CONFIG_SMP
+#include <linux/sched.h>
+
/* Dummy stub. Though we may check XEN_RESCHEDULE_VECTOR before __do_IRQ,
* it ends up to issue several memory accesses upon percpu data and
* thus adds unnecessary traffic to other paths.
@@ -99,7 +101,13 @@ static int xen_slab_ready;
static irqreturn_t
xen_dummy_handler(int irq, void *dev_id)
{
+ return IRQ_HANDLED;
+}
+static irqreturn_t
+xen_resched_handler(int irq, void *dev_id)
+{
+ scheduler_ipi();
return IRQ_HANDLED;
}
@@ -110,7 +118,7 @@ static struct irqaction xen_ipi_irqactio
};
static struct irqaction xen_resched_irqaction = {
- .handler = xen_dummy_handler,
+ .handler = xen_resched_handler,
.flags = IRQF_DISABLED,
.name = "resched"
};
Index: linux-2.6/arch/m32r/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/m32r/kernel/smp.c
+++ linux-2.6/arch/m32r/kernel/smp.c
@@ -122,8 +122,6 @@ void smp_send_reschedule(int cpu_id)
*
* Description: This routine executes on CPU which received
* 'RESCHEDULE_IPI'.
- * Rescheduling is processed at the exit of interrupt
- * operation.
*
* Born on Date: 2002.02.05
*
@@ -138,7 +136,7 @@ void smp_send_reschedule(int cpu_id)
*==========================================================================*/
void smp_reschedule_interrupt(void)
{
- /* nothing to do */
+ scheduler_ipi();
}
/*==========================================================================*
Index: linux-2.6/arch/mips/kernel/smtc.c
===================================================================
--- linux-2.6.orig/arch/mips/kernel/smtc.c
+++ linux-2.6/arch/mips/kernel/smtc.c
@@ -930,7 +930,7 @@ static void post_direct_ipi(int cpu, str
static void ipi_resched_interrupt(void)
{
- /* Return from interrupt should be enough to cause scheduler check */
+ scheduler_ipi();
}
static void ipi_call_interrupt(void)
Index: linux-2.6/arch/mips/sibyte/bcm1480/smp.c
===================================================================
--- linux-2.6.orig/arch/mips/sibyte/bcm1480/smp.c
+++ linux-2.6/arch/mips/sibyte/bcm1480/smp.c
@@ -20,6 +20,7 @@
#include <linux/delay.h>
#include <linux/smp.h>
#include <linux/kernel_stat.h>
+#include <linux/sched.h>
#include <asm/mmu_context.h>
#include <asm/io.h>
@@ -189,10 +190,8 @@ void bcm1480_mailbox_interrupt(void)
/* Clear the mailbox to clear the interrupt */
__raw_writeq(((u64)action)<<48, mailbox_0_clear_regs[cpu]);
- /*
- * Nothing to do for SMP_RESCHEDULE_YOURSELF; returning from the
- * interrupt will do the reschedule for us
- */
+ if (actione & SMP_RESCHEDULE_YOURSELF)
+ scheduler_ipi();
if (action & SMP_CALL_FUNCTION)
smp_call_function_interrupt();
Index: linux-2.6/arch/mips/sibyte/sb1250/smp.c
===================================================================
--- linux-2.6.orig/arch/mips/sibyte/sb1250/smp.c
+++ linux-2.6/arch/mips/sibyte/sb1250/smp.c
@@ -21,6 +21,7 @@
#include <linux/interrupt.h>
#include <linux/smp.h>
#include <linux/kernel_stat.h>
+#include <linux/sched.h>
#include <asm/mmu_context.h>
#include <asm/io.h>
@@ -177,10 +178,8 @@ void sb1250_mailbox_interrupt(void)
/* Clear the mailbox to clear the interrupt */
____raw_writeq(((u64)action) << 48, mailbox_clear_regs[cpu]);
- /*
- * Nothing to do for SMP_RESCHEDULE_YOURSELF; returning from the
- * interrupt will do the reschedule for us
- */
+ if (action & SMP_RESCHEDULE_YOURSELF)
+ scheduler_ipi();
if (action & SMP_CALL_FUNCTION)
smp_call_function_interrupt();
Index: linux-2.6/arch/mn10300/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/mn10300/kernel/smp.c
+++ linux-2.6/arch/mn10300/kernel/smp.c
@@ -464,14 +464,11 @@ void smp_send_stop(void)
* @irq: The interrupt number.
* @dev_id: The device ID.
*
- * We need do nothing here, since the scheduling will be effected on our way
- * back through entry.S.
- *
* Returns IRQ_HANDLED to indicate we handled the interrupt successfully.
*/
static irqreturn_t smp_reschedule_interrupt(int irq, void *dev_id)
{
- /* do nothing */
+ scheduler_ipi();
return IRQ_HANDLED;
}
Index: linux-2.6/arch/parisc/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/parisc/kernel/smp.c
+++ linux-2.6/arch/parisc/kernel/smp.c
@@ -155,10 +155,7 @@ ipi_interrupt(int irq, void *dev_id)
case IPI_RESCHEDULE:
smp_debug(100, KERN_DEBUG "CPU%d
IPI_RESCHEDULE\n", this_cpu);
- /*
- * Reschedule callback. Everything to be
- * done is done by the interrupt return path.
- */
+ scheduler_ipi();
break;
case IPI_CALL_FUNC:
Index: linux-2.6/arch/powerpc/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/powerpc/kernel/smp.c
+++ linux-2.6/arch/powerpc/kernel/smp.c
@@ -127,7 +127,7 @@ static irqreturn_t call_function_action(
static irqreturn_t reschedule_action(int irq, void *data)
{
- /* we just need the return path side effect of checking need_resched */
+ scheduler_ipi();
return IRQ_HANDLED;
}
Index: linux-2.6/arch/s390/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/s390/kernel/smp.c
+++ linux-2.6/arch/s390/kernel/smp.c
@@ -163,12 +163,12 @@ static void do_ext_call_interrupt(unsign
/*
* handle bit signal external calls
- *
- * For the ec_schedule signal we have to do nothing. All the work
- * is done automatically when we return from the interrupt.
*/
bits = xchg(&S390_lowcore.ext_call_fast, 0);
+ if (test_bit(ec_schedule, &bits))
+ scheduler_ipi();
+
if (test_bit(ec_call_function, &bits))
generic_smp_call_function_interrupt();
Index: linux-2.6/arch/sh/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/sh/kernel/smp.c
+++ linux-2.6/arch/sh/kernel/smp.c
@@ -20,6 +20,7 @@
#include <linux/module.h>
#include <linux/cpu.h>
#include <linux/interrupt.h>
+#include <linux/sched.h>
#include <asm/atomic.h>
#include <asm/processor.h>
#include <asm/system.h>
@@ -323,6 +324,7 @@ void smp_message_recv(unsigned int msg)
generic_smp_call_function_interrupt();
break;
case SMP_MSG_RESCHEDULE:
+ scheduler_ipi();
break;
case SMP_MSG_FUNCTION_SINGLE:
generic_smp_call_function_single_interrupt();
Index: linux-2.6/arch/sparc/kernel/smp_32.c
===================================================================
--- linux-2.6.orig/arch/sparc/kernel/smp_32.c
+++ linux-2.6/arch/sparc/kernel/smp_32.c
@@ -125,7 +125,7 @@ struct linux_prom_registers smp_penguin_
void smp_send_reschedule(int cpu)
{
- /* See sparc64 */
+ scheduler_ipi();
}
void smp_send_stop(void)
Index: linux-2.6/arch/sparc/kernel/smp_64.c
===================================================================
--- linux-2.6.orig/arch/sparc/kernel/smp_64.c
+++ linux-2.6/arch/sparc/kernel/smp_64.c
@@ -1369,6 +1369,7 @@ void smp_send_reschedule(int cpu)
void __irq_entry smp_receive_signal_client(int irq, struct pt_regs *regs)
{
clear_softint(1 << irq);
+ scheduler_ipi();
}
/* This is a nop because we capture all other cpus
Index: linux-2.6/arch/tile/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/tile/kernel/smp.c
+++ linux-2.6/arch/tile/kernel/smp.c
@@ -184,12 +184,8 @@ void flush_icache_range(unsigned long st
/* Called when smp_send_reschedule() triggers IRQ_RESCHEDULE. */
static irqreturn_t handle_reschedule_ipi(int irq, void *token)
{
- /*
- * Nothing to do here; when we return from interrupt, the
- * rescheduling will occur there. But do bump the interrupt
- * profiler count in the meantime.
- */
__get_cpu_var(irq_stat).irq_resched_count++;
+ scheduler_ipi();
return IRQ_HANDLED;
}
Index: linux-2.6/arch/um/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/um/kernel/smp.c
+++ linux-2.6/arch/um/kernel/smp.c
@@ -173,7 +173,7 @@ void IPI_handler(int cpu)
break;
case 'R':
- set_tsk_need_resched(current);
+ scheduler_ipi();
break;
case 'S':
Index: linux-2.6/arch/x86/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/smp.c
+++ linux-2.6/arch/x86/kernel/smp.c
@@ -194,14 +194,13 @@ static void native_stop_other_cpus(int w
}
/*
- * Reschedule call back. Nothing to do,
- * all the work is done automatically when
- * we return from the interrupt.
+ * Reschedule call back.
*/
void smp_reschedule_interrupt(struct pt_regs *regs)
{
ack_APIC_irq();
inc_irq_stat(irq_resched_count);
+ scheduler_ipi();
/*
* KVM uses this interrupt to force a cpu out of guest mode
*/
Index: linux-2.6/arch/x86/xen/smp.c
===================================================================
--- linux-2.6.orig/arch/x86/xen/smp.c
+++ linux-2.6/arch/x86/xen/smp.c
@@ -46,13 +46,12 @@ static irqreturn_t xen_call_function_int
static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id);
/*
- * Reschedule call back. Nothing to do,
- * all the work is done automatically when
- * we return from the interrupt.
+ * Reschedule call back.
*/
static irqreturn_t xen_reschedule_interrupt(int irq, void *dev_id)
{
inc_irq_stat(irq_resched_count);
+ scheduler_ipi();
return IRQ_HANDLED;
}
Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -2183,6 +2183,7 @@ extern void set_task_comm(struct task_st
extern char *get_task_comm(char *to, struct task_struct *tsk);
#ifdef CONFIG_SMP
+static inline void scheduler_ipi(void) { }
extern unsigned long wait_task_inactive(struct task_struct *, long
match_state);
#else
static inline unsigned long wait_task_inactive(struct task_struct *p,
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