From d04c56f73c30a5e593202ecfcf25ed43d42363a2 Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Wed, 4 Oct 2006 16:47:49 +1000 Subject: [POWERPC] Lazy interrupt disabling for 64-bit machines This implements a lazy strategy for disabling interrupts. This means that local_irq_disable() et al. just clear the 'interrupts are enabled' flag in the paca. If an interrupt comes along, the interrupt entry code notices that interrupts are supposed to be disabled, and clears the EE bit in SRR1, clears the 'interrupts are hard-enabled' flag in the paca, and returns. This means that interrupts only actually get disabled in the processor when an interrupt comes along. When interrupts are enabled by local_irq_enable() et al., the code sets the interrupts-enabled flag in the paca, and then checks whether interrupts got hard-disabled. If so, it also sets the EE bit in the MSR to hard-enable the interrupts. This has the potential to improve performance, and also makes it easier to make a kernel that can boot on iSeries and on other 64-bit machines, since this lazy-disable strategy is very similar to the soft-disable strategy that iSeries already uses. This version renames paca->proc_enabled to paca->soft_enabled, and changes a couple of soft-disables in the kexec code to hard-disables, which should fix the crash that Michael Ellerman saw. This doesn't yet use a reserved CR field for the soft_enabled and hard_enabled flags. This applies on top of Stephen Rothwell's patches to make it possible to build a combined iSeries/other kernel. Signed-off-by: Paul Mackerras --- arch/powerpc/kernel/irq.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) (limited to 'arch/powerpc/kernel/irq.c') diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c index 5e37bf14ef2d..67b21a008f6e 100644 --- a/arch/powerpc/kernel/irq.c +++ b/arch/powerpc/kernel/irq.c @@ -64,8 +64,9 @@ #include #include #include -#ifdef CONFIG_PPC_ISERIES +#ifdef CONFIG_PPC64 #include +#include #endif int __irq_offset_value; @@ -95,6 +96,27 @@ extern atomic_t ipi_sent; EXPORT_SYMBOL(irq_desc); int distribute_irqs = 1; + +void local_irq_restore(unsigned long en) +{ + get_paca()->soft_enabled = en; + if (!en) + return; + + if (firmware_has_feature(FW_FEATURE_ISERIES)) { + if (get_paca()->lppaca_ptr->int_dword.any_int) + iseries_handle_interrupts(); + return; + } + + if (get_paca()->hard_enabled) + return; + /* need to hard-enable interrupts here */ + get_paca()->hard_enabled = en; + if ((int)mfspr(SPRN_DEC) < 0) + mtspr(SPRN_DEC, 1); + hard_irq_enable(); +} #endif /* CONFIG_PPC64 */ int show_interrupts(struct seq_file *p, void *v) -- cgit v1.2.2 From 5414c6be57dd02e089c3eba1f5134f441733d013 Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Tue, 24 Oct 2006 13:37:34 +1000 Subject: [POWERPC] Make irq_dispose_mapping(NO_IRQ) a nop It makes for a friendlier API if irq_dispose_mapping(NO_IRQ) is a nop, rather than triggering a WARN_ON. Signed-off-by: Michael Ellerman Acked-by: Benjamin Herrenschmidt Signed-off-by: Paul Mackerras --- arch/powerpc/kernel/irq.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'arch/powerpc/kernel/irq.c') diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c index 67b21a008f6e..eb9fc621e057 100644 --- a/arch/powerpc/kernel/irq.c +++ b/arch/powerpc/kernel/irq.c @@ -648,10 +648,14 @@ EXPORT_SYMBOL_GPL(irq_of_parse_and_map); void irq_dispose_mapping(unsigned int virq) { - struct irq_host *host = irq_map[virq].host; + struct irq_host *host; irq_hw_number_t hwirq; unsigned long flags; + if (virq == NO_IRQ) + return; + + host = irq_map[virq].host; WARN_ON (host == NULL); if (host == NULL) return; -- cgit v1.2.2 From b06a318372ba95873abfe323076bd7e115d64b67 Mon Sep 17 00:00:00 2001 From: Stephen Rothwell Date: Tue, 21 Nov 2006 14:16:13 +1100 Subject: [POWERPC] iSeries: fix irq.c for combined build Signed-off-by: Stephen Rothwell Signed-off-by: Paul Mackerras --- arch/powerpc/kernel/irq.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'arch/powerpc/kernel/irq.c') diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c index eb9fc621e057..e1936952017c 100644 --- a/arch/powerpc/kernel/irq.c +++ b/arch/powerpc/kernel/irq.c @@ -268,7 +268,8 @@ void do_IRQ(struct pt_regs *regs) set_irq_regs(old_regs); #ifdef CONFIG_PPC_ISERIES - if (get_lppaca()->int_dword.fields.decr_int) { + if (firmware_has_feature(FW_FEATURE_ISERIES) && + get_lppaca()->int_dword.fields.decr_int) { get_lppaca()->int_dword.fields.decr_int = 0; /* Signal a fake decrementer interrupt */ timer_interrupt(regs); -- cgit v1.2.2 From ef2b343e99e772e35f0f9d00f7db318b6629c16e Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Fri, 10 Nov 2006 21:32:40 +0000 Subject: [POWERPC] Make soft_enabled irqs preempt safe Rewrite local_get_flags and local_irq_disable to use r13 explicitly, to avoid the risk that gcc will split get_paca()->soft_enabled into a sequence unsafe against preemption. Similar care in local_irq_restore. Signed-off-by: Hugh Dickins Signed-off-by: Paul Mackerras --- arch/powerpc/kernel/irq.c | 57 ++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 52 insertions(+), 5 deletions(-) (limited to 'arch/powerpc/kernel/irq.c') diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c index e1936952017c..0bd8c7665834 100644 --- a/arch/powerpc/kernel/irq.c +++ b/arch/powerpc/kernel/irq.c @@ -97,22 +97,69 @@ EXPORT_SYMBOL(irq_desc); int distribute_irqs = 1; +static inline unsigned long get_hard_enabled(void) +{ + unsigned long enabled; + + __asm__ __volatile__("lbz %0,%1(13)" + : "=r" (enabled) : "i" (offsetof(struct paca_struct, hard_enabled))); + + return enabled; +} + +static inline void set_soft_enabled(unsigned long enable) +{ + __asm__ __volatile__("stb %0,%1(13)" + : : "r" (enable), "i" (offsetof(struct paca_struct, soft_enabled))); +} + void local_irq_restore(unsigned long en) { - get_paca()->soft_enabled = en; + /* + * get_paca()->soft_enabled = en; + * Is it ever valid to use local_irq_restore(0) when soft_enabled is 1? + * That was allowed before, and in such a case we do need to take care + * that gcc will set soft_enabled directly via r13, not choose to use + * an intermediate register, lest we're preempted to a different cpu. + */ + set_soft_enabled(en); if (!en) return; if (firmware_has_feature(FW_FEATURE_ISERIES)) { - if (get_paca()->lppaca_ptr->int_dword.any_int) + /* + * Do we need to disable preemption here? Not really: in the + * unlikely event that we're preempted to a different cpu in + * between getting r13, loading its lppaca_ptr, and loading + * its any_int, we might call iseries_handle_interrupts without + * an interrupt pending on the new cpu, but that's no disaster, + * is it? And the business of preempting us off the old cpu + * would itself involve a local_irq_restore which handles the + * interrupt to that cpu. + * + * But use "local_paca->lppaca_ptr" instead of "get_lppaca()" + * to avoid any preemption checking added into get_paca(). + */ + if (local_paca->lppaca_ptr->int_dword.any_int) iseries_handle_interrupts(); return; } - if (get_paca()->hard_enabled) + /* + * if (get_paca()->hard_enabled) return; + * But again we need to take care that gcc gets hard_enabled directly + * via r13, not choose to use an intermediate register, lest we're + * preempted to a different cpu in between the two instructions. + */ + if (get_hard_enabled()) return; - /* need to hard-enable interrupts here */ - get_paca()->hard_enabled = en; + + /* + * Need to hard-enable interrupts here. Since currently disabled, + * no need to take further asm precautions against preemption; but + * use local_paca instead of get_paca() to avoid preemption checking. + */ + local_paca->hard_enabled = en; if ((int)mfspr(SPRN_DEC) < 0) mtspr(SPRN_DEC, 1); hard_irq_enable(); -- cgit v1.2.2