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x86 mmiotrace: dynamically disable non-boot CPUs
From 8979ee55cb6a429c4edd72ebec2244b849f6a79a Mon Sep 17 00:00:00 2001 From: Pekka Paalanen <pq@iki.fi> Date: Sat, 12 Apr 2008 00:18:57 +0300 Mmiotrace is not reliable with multiple CPUs and may miss events. Drop to single CPU when mmiotrace is activated. Signed-off-by: Pekka Paalanen <pq@iki.fi> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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1 changed files with 61 additions and 0 deletions
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@ -32,6 +32,7 @@
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#include <asm/e820.h> /* for ISA_START_ADDRESS */
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#include <asm/atomic.h>
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#include <linux/percpu.h>
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#include <linux/cpu.h>
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#include "pf_in.h"
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@ -400,6 +401,64 @@ static void clear_trace_list(void)
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}
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}
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#ifdef CONFIG_HOTPLUG_CPU
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static cpumask_t downed_cpus;
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static void enter_uniprocessor(void)
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{
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int cpu;
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int err;
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get_online_cpus();
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downed_cpus = cpu_online_map;
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cpu_clear(first_cpu(cpu_online_map), downed_cpus);
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if (num_online_cpus() > 1)
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pr_notice(NAME "Disabling non-boot CPUs...\n");
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put_online_cpus();
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for_each_cpu_mask(cpu, downed_cpus) {
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err = cpu_down(cpu);
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if (!err) {
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pr_info(NAME "CPU%d is down.\n", cpu);
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} else {
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pr_err(NAME "Error taking CPU%d down: %d\n", cpu, err);
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}
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}
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if (num_online_cpus() > 1)
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pr_warning(NAME "multiple CPUs still online, "
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"may miss events.\n");
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}
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static void leave_uniprocessor(void)
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{
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int cpu;
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int err;
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if (cpus_weight(downed_cpus) == 0)
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return;
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pr_notice(NAME "Re-enabling CPUs...\n");
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for_each_cpu_mask(cpu, downed_cpus) {
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err = cpu_up(cpu);
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if (!err)
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pr_info(NAME "enabled CPU%d.\n", cpu);
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else
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pr_err(NAME "cannot re-enable CPU%d: %d\n", cpu, err);
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}
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}
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#else /* !CONFIG_HOTPLUG_CPU */
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static void enter_uniprocessor(void)
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{
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if (num_online_cpus() > 1)
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pr_warning(NAME "multiple CPUs are online, may miss events. "
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"Suggest booting with maxcpus=1 kernel argument.\n");
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}
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static void leave_uniprocessor(void)
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{
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}
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#endif
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#if 0 /* XXX: out of order */
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static struct file_operations fops_marker = {
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.owner = THIS_MODULE,
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@ -422,6 +481,7 @@ void enable_mmiotrace(void)
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if (nommiotrace)
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pr_info(NAME "MMIO tracing disabled.\n");
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enter_uniprocessor();
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spin_lock_irq(&trace_lock);
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atomic_inc(&mmiotrace_enabled);
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spin_unlock_irq(&trace_lock);
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@ -442,6 +502,7 @@ void disable_mmiotrace(void)
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spin_unlock_irq(&trace_lock);
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clear_trace_list(); /* guarantees: no more kmmio callbacks */
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leave_uniprocessor();
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if (marker_file) {
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debugfs_remove(marker_file);
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marker_file = NULL;
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