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Subject[PATCH 7/9] cpumask: avoid cpumask games in arch/x86/kernel/cpu/cpufreq/speedstep-centrino.c

Impact: don't play with current's cpumask

It's generally a very bad idea to mug some process's cpumask: it could
legitimately and reasonably be changed by root, which could break us
(if done before our code) or them (if we restore the wrong value).

Use rdmsr_on_cpu and wrmsr_on_cpu instead.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
To: davej@redhat.com
To: cpufreq@vger.kernel.org
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
---
arch/x86/kernel/cpu/cpufreq/speedstep-centrino.c | 60 ++++++-----------------
1 file changed, 17 insertions(+), 43 deletions(-)
diff --git a/arch/x86/kernel/cpu/cpufreq/speedstep-centrino.c b/arch/x86/kernel/cpu/cpufreq/speedstep-centrino.c
--- a/arch/x86/kernel/cpu/cpufreq/speedstep-centrino.c
+++ b/arch/x86/kernel/cpu/cpufreq/speedstep-centrino.c
@@ -323,14 +323,8 @@ static unsigned int get_cur_freq(unsigne
{
unsigned l, h;
unsigned clock_freq;
- cpumask_t saved_mask;

- saved_mask = current->cpus_allowed;
- set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
- if (smp_processor_id() != cpu)
- return 0;
-
- rdmsr(MSR_IA32_PERF_STATUS, l, h);
+ rdmsr_on_cpu(cpu, MSR_IA32_PERF_STATUS, &l, &h);
clock_freq = extract_clock(l, cpu, 0);

if (unlikely(clock_freq == 0)) {
@@ -340,11 +334,9 @@ static unsigned int get_cur_freq(unsigne
* P-state transition (like TM2). Get the last freq set
* in PERF_CTL.
*/
- rdmsr(MSR_IA32_PERF_CTL, l, h);
+ rdmsr_on_cpu(cpu, MSR_IA32_PERF_CTL, &l, &h);
clock_freq = extract_clock(l, cpu, 1);
}
-
- set_cpus_allowed_ptr(current, &saved_mask);
return clock_freq;
}

@@ -467,15 +459,10 @@ static int centrino_target (struct cpufr
struct cpufreq_freqs freqs;
int retval = 0;
unsigned int j, k, first_cpu, tmp;
- cpumask_var_t saved_mask, covered_cpus;
+ cpumask_var_t covered_cpus;

- if (unlikely(!alloc_cpumask_var(&saved_mask, GFP_KERNEL)))
+ if (unlikely(!alloc_cpumask_var(&covered_cpus, GFP_KERNEL)))
return -ENOMEM;
- if (unlikely(!alloc_cpumask_var(&covered_cpus, GFP_KERNEL))) {
- free_cpumask_var(saved_mask);
- return -ENOMEM;
- }
- cpumask_copy(saved_mask, &current->cpus_allowed);

if (unlikely(per_cpu(centrino_model, cpu) == NULL)) {
retval = -ENODEV;
@@ -493,7 +480,7 @@ static int centrino_target (struct cpufr

first_cpu = 1;
for_each_cpu(j, policy->cpus) {
- const struct cpumask *mask;
+ int good_cpu;

/* cpufreq holds the hotplug lock, so we are safe here */
if (!cpu_online(j))
@@ -504,32 +491,30 @@ static int centrino_target (struct cpufr
* Make sure we are running on CPU that wants to change freq
*/
if (policy->shared_type == CPUFREQ_SHARED_TYPE_ANY)
- mask = policy->cpus;
+ good_cpu = cpumask_any_and(policy->cpus,
+ cpu_online_mask);
else
- mask = cpumask_of(j);
+ good_cpu = j;

- set_cpus_allowed_ptr(current, mask);
- preempt_disable();
- if (unlikely(!cpu_isset(smp_processor_id(), *mask))) {
+ if (good_cpu >= nr_cpu_ids) {
dprintk("couldn't limit to CPUs in this domain\n");
retval = -EAGAIN;
if (first_cpu) {
/* We haven't started the transition yet. */
- goto migrate_end;
+ goto out;
}
- preempt_enable();
break;
}

msr = per_cpu(centrino_model, cpu)->op_points[newstate].index;

if (first_cpu) {
- rdmsr(MSR_IA32_PERF_CTL, oldmsr, h);
+ rdmsr_on_cpu(good_cpu, MSR_IA32_PERF_CTL, &oldmsr, &h);
if (msr == (oldmsr & 0xffff)) {
dprintk("no change needed - msr was and needs "
"to be %x\n", oldmsr);
retval = 0;
- goto migrate_end;
+ goto out;
}

freqs.old = extract_clock(oldmsr, cpu, 0);
@@ -553,14 +538,11 @@ static int centrino_target (struct cpufr
oldmsr |= msr;
}

- wrmsr(MSR_IA32_PERF_CTL, oldmsr, h);
- if (policy->shared_type == CPUFREQ_SHARED_TYPE_ANY) {
- preempt_enable();
+ wrmsr_on_cpu(good_cpu, MSR_IA32_PERF_CTL, oldmsr, h);
+ if (policy->shared_type == CPUFREQ_SHARED_TYPE_ANY)
break;
- }

- cpu_set(j, *covered_cpus);
- preempt_enable();
+ cpumask_set_cpu(j, covered_cpus);
}

for_each_cpu(k, policy->cpus) {
@@ -578,10 +560,8 @@ static int centrino_target (struct cpufr
* Best effort undo..
*/

- for_each_cpu_mask_nr(j, *covered_cpus) {
- set_cpus_allowed_ptr(current, &cpumask_of_cpu(j));
- wrmsr(MSR_IA32_PERF_CTL, oldmsr, h);
- }
+ for_each_cpu(j, covered_cpus)
+ wrmsr_on_cpu(j, MSR_IA32_PERF_CTL, oldmsr, h);

tmp = freqs.new;
freqs.new = freqs.old;
@@ -593,15 +573,9 @@ static int centrino_target (struct cpufr
cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
}
}
- set_cpus_allowed_ptr(current, saved_mask);
retval = 0;
- goto out;

-migrate_end:
- preempt_enable();
- set_cpus_allowed_ptr(current, saved_mask);
out:
- free_cpumask_var(saved_mask);
free_cpumask_var(covered_cpus);
return retval;
}


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