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 <pet...@infradead.org> 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.zijls...@chello.nl> 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, _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev