diff options
Diffstat (limited to 'arch/x86_64/kernel/genapic_flat.c')
| -rw-r--r-- | arch/x86_64/kernel/genapic_flat.c | 110 |
1 files changed, 94 insertions, 16 deletions
diff --git a/arch/x86_64/kernel/genapic_flat.c b/arch/x86_64/kernel/genapic_flat.c index b4cbbad0422..28284696508 100644 --- a/arch/x86_64/kernel/genapic_flat.c +++ b/arch/x86_64/kernel/genapic_flat.c @@ -7,6 +7,8 @@ * Hacked for x86-64 by James Cleverdon from i386 architecture code by * Martin Bligh, Andi Kleen, James Bottomley, John Stultz, and * James Cleverdon. + * Ashok Raj <ashok.raj@intel.com> + * Removed IPI broadcast shortcut to support CPU hotplug */ #include <linux/config.h> #include <linux/threads.h> @@ -18,6 +20,46 @@ #include <asm/smp.h> #include <asm/ipi.h> +/* + * The following permit choosing broadcast IPI shortcut v.s sending IPI only + * to online cpus via the send_IPI_mask varient. + * The mask version is my preferred option, since it eliminates a lot of + * other extra code that would need to be written to cleanup intrs sent + * to a CPU while offline. + * + * Sending broadcast introduces lots of trouble in CPU hotplug situations. + * These IPI's are delivered to cpu's irrespective of their offline status + * and could pickup stale intr data when these CPUS are turned online. + * + * Not using broadcast is a cleaner approach IMO, but Andi Kleen disagrees with + * the idea of not using broadcast IPI's anymore. Hence the run time check + * is introduced, on his request so we can choose an alternate mechanism. + * + * Initial wacky performance tests that collect cycle counts show + * no increase in using mask v.s broadcast version. In fact they seem + * identical in terms of cycle counts. + * + * if we need to use broadcast, we need to do the following. + * + * cli; + * hold call_lock; + * clear any pending IPI, just ack and clear all pending intr + * set cpu_online_map; + * release call_lock; + * sti; + * + * The complicated dummy irq processing shown above is not required if + * we didnt sent IPI's to wrong CPU's in the first place. + * + * - Ashok Raj <ashok.raj@intel.com> + */ +#ifdef CONFIG_HOTPLUG_CPU +#define DEFAULT_SEND_IPI (1) +#else +#define DEFAULT_SEND_IPI (0) +#endif + +static int no_broadcast=DEFAULT_SEND_IPI; static cpumask_t flat_target_cpus(void) { @@ -45,22 +87,6 @@ static void flat_init_apic_ldr(void) apic_write_around(APIC_LDR, val); } -static void flat_send_IPI_allbutself(int vector) -{ - /* - * if there are no other CPUs in the system then - * we get an APIC send error if we try to broadcast. - * thus we have to avoid sending IPIs in this case. - */ - if (num_online_cpus() > 1) - __send_IPI_shortcut(APIC_DEST_ALLBUT, vector, APIC_DEST_LOGICAL); -} - -static void flat_send_IPI_all(int vector) -{ - __send_IPI_shortcut(APIC_DEST_ALLINC, vector, APIC_DEST_LOGICAL); -} - static void flat_send_IPI_mask(cpumask_t cpumask, int vector) { unsigned long mask = cpus_addr(cpumask)[0]; @@ -93,6 +119,39 @@ static void flat_send_IPI_mask(cpumask_t cpumask, int vector) local_irq_restore(flags); } +static inline void __local_flat_send_IPI_allbutself(int vector) +{ + if (no_broadcast) { + cpumask_t mask = cpu_online_map; + int this_cpu = get_cpu(); + + cpu_clear(this_cpu, mask); + flat_send_IPI_mask(mask, vector); + put_cpu(); + } + else + __send_IPI_shortcut(APIC_DEST_ALLBUT, vector, APIC_DEST_LOGICAL); +} + +static inline void __local_flat_send_IPI_all(int vector) +{ + if (no_broadcast) + flat_send_IPI_mask(cpu_online_map, vector); + else + __send_IPI_shortcut(APIC_DEST_ALLINC, vector, APIC_DEST_LOGICAL); +} + +static void flat_send_IPI_allbutself(int vector) +{ + if (((num_online_cpus()) - 1) >= 1) + __local_flat_send_IPI_allbutself(vector); +} + +static void flat_send_IPI_all(int vector) +{ + __local_flat_send_IPI_all(vector); +} + static int flat_apic_id_registered(void) { return physid_isset(GET_APIC_ID(apic_read(APIC_ID)), phys_cpu_present_map); @@ -111,6 +170,16 @@ static unsigned int phys_pkg_id(int index_msb) return ((ebx >> 24) & 0xFF) >> index_msb; } +static __init int no_ipi_broadcast(char *str) +{ + get_option(&str, &no_broadcast); + printk ("Using %s mode\n", no_broadcast ? "No IPI Broadcast" : + "IPI Broadcast"); + return 1; +} + +__setup("no_ipi_broadcast", no_ipi_broadcast); + struct genapic apic_flat = { .name = "flat", .int_delivery_mode = dest_LowestPrio, @@ -125,3 +194,12 @@ struct genapic apic_flat = { .cpu_mask_to_apicid = flat_cpu_mask_to_apicid, .phys_pkg_id = phys_pkg_id, }; + +static int __init print_ipi_mode(void) +{ + printk ("Using IPI %s mode\n", no_broadcast ? "No-Shortcut" : + "Shortcut"); + return 0; +} + +late_initcall(print_ipi_mode); |