From 6ae56b55bc364bc2f2342f599b46581627ba22da Mon Sep 17 00:00:00 2001 From: Robert Richter Date: Thu, 29 Apr 2010 14:55:55 +0200 Subject: [PATCH] oprofile/x86: protect cpu hotplug sections This patch reworks oprofile cpu hotplug code as follows: Introduce ctr_running variable to check, if counters are running or not. The state must be known for taking a cpu on or offline and when switching counters during counter multiplexing. Protect on_each_cpu() sections with get_online_cpus()/put_online_cpu() functions. This is necessary if notifiers or states are modified. Within these sections the cpu mask may not change. Switch only between counters in nmi_cpu_switch(), if counters are running. Otherwise the switch may restart a counter though they are disabled. Add nmi_cpu_setup() and nmi_cpu_shutdown() to cpu hotplug code. The function must also be called to avoid uninitialzed counter usage. Cc: Andi Kleen Signed-off-by: Robert Richter --- arch/x86/oprofile/nmi_int.c | 52 +++++++++++++++++++++++++++++++++++++++------ 1 file changed, 46 insertions(+), 6 deletions(-) diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c index c5df8ee..b56601e 100644 --- a/arch/x86/oprofile/nmi_int.c +++ b/arch/x86/oprofile/nmi_int.c @@ -31,8 +31,9 @@ static struct op_x86_model_spec *model; static DEFINE_PER_CPU(struct op_msrs, cpu_msrs); static DEFINE_PER_CPU(unsigned long, saved_lvtpc); -/* 0 == registered but off, 1 == registered and on */ -static int nmi_enabled = 0; +/* must be protected with get_online_cpus()/put_online_cpus(): */ +static int nmi_enabled; +static int ctr_running; struct op_counter_config counter_config[OP_MAX_COUNTER]; @@ -103,7 +104,10 @@ static void nmi_cpu_start(void *dummy) static int nmi_start(void) { + get_online_cpus(); on_each_cpu(nmi_cpu_start, NULL, 1); + ctr_running = 1; + put_online_cpus(); return 0; } @@ -118,7 +122,10 @@ static void nmi_cpu_stop(void *dummy) static void nmi_stop(void) { + get_online_cpus(); on_each_cpu(nmi_cpu_stop, NULL, 1); + ctr_running = 0; + put_online_cpus(); } #ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX @@ -258,7 +265,10 @@ static int nmi_switch_event(void) if (nmi_multiplex_on() < 0) return -EINVAL; /* not necessary */ - on_each_cpu(nmi_cpu_switch, NULL, 1); + get_online_cpus(); + if (ctr_running) + on_each_cpu(nmi_cpu_switch, NULL, 1); + put_online_cpus(); return 0; } @@ -386,8 +396,11 @@ static int nmi_setup(void) if (err) goto fail; + get_online_cpus(); on_each_cpu(nmi_cpu_setup, NULL, 1); nmi_enabled = 1; + put_online_cpus(); + return 0; fail: free_msrs(); @@ -433,8 +446,11 @@ static void nmi_shutdown(void) { struct op_msrs *msrs; - nmi_enabled = 0; + get_online_cpus(); on_each_cpu(nmi_cpu_shutdown, NULL, 1); + nmi_enabled = 0; + ctr_running = 0; + put_online_cpus(); unregister_die_notifier(&profile_exceptions_nb); msrs = &get_cpu_var(cpu_msrs); model->shutdown(msrs); @@ -442,6 +458,22 @@ static void nmi_shutdown(void) put_cpu_var(cpu_msrs); } +static void nmi_cpu_up(void *dummy) +{ + if (nmi_enabled) + nmi_cpu_setup(dummy); + if (ctr_running) + nmi_cpu_start(dummy); +} + +static void nmi_cpu_down(void *dummy) +{ + if (ctr_running) + nmi_cpu_stop(dummy); + if (nmi_enabled) + nmi_cpu_shutdown(dummy); +} + static int nmi_create_files(struct super_block *sb, struct dentry *root) { unsigned int i; @@ -478,10 +510,10 @@ static int oprofile_cpu_notifier(struct notifier_block *b, unsigned long action, switch (action) { case CPU_DOWN_FAILED: case CPU_ONLINE: - smp_call_function_single(cpu, nmi_cpu_start, NULL, 0); + smp_call_function_single(cpu, nmi_cpu_up, NULL, 0); break; case CPU_DOWN_PREPARE: - smp_call_function_single(cpu, nmi_cpu_stop, NULL, 1); + smp_call_function_single(cpu, nmi_cpu_down, NULL, 1); break; } return NOTIFY_DONE; @@ -699,7 +731,11 @@ int __init op_nmi_init(struct oprofile_operations *ops) return -ENODEV; } + get_online_cpus(); register_cpu_notifier(&oprofile_cpu_nb); + nmi_enabled = 0; + ctr_running = 0; + put_online_cpus(); /* default values, can be overwritten by model */ ops->create_files = nmi_create_files; @@ -729,7 +765,11 @@ void op_nmi_exit(void) { if (using_nmi) { exit_sysfs(); + get_online_cpus(); unregister_cpu_notifier(&oprofile_cpu_nb); + nmi_enabled = 0; + ctr_running = 0; + put_online_cpus(); } if (model->exit) model->exit(); -- 2.7.4