Re: [PATCH 4/6] x86/cpufreq: use cpumask_copy instead of =

Rusty Russell
2009-06-10T06:22:59Z

On Wed, 10 Jun 2009 01:16:44 am Linus Torvalds wrote:
> On Tue, 9 Jun 2009, Rusty Russell wrote:
> > for_each_online_cpu(i) {
> > - if (check_supported_cpu(i))
> > + if (work_on_cpu(i, check_supported_cpu, NULL) == 0)
> > supported_cpus++;
>
> Please STOP USING THAT HORRIBLE "work_on_cpu()" crap.
>
> Is there any reason you do that? We've had to fix up the fallout from that
> kind of crazy crap several times.

Simplicity of translation, laziness, and reluctance to break stuff. And a
nicer API.

It's called here on cpu bringup, but I'll change it (the code doesn't sleep).
I've a couple of others in my queue I'll look at similarly.

powernow_k8_target is problematic: it grabs a mutex. cpufreq people, is this
called often?

Thanks,
Rusty.

Subject: cpumask: avoid playing with cpus_allowed in powernow-k8.c
From: Rusty Russell <rusty@rustcorp.com.au>

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).

I use work_on_cpu, which is slightly less efficient than the old code,
but the code is complex enough that using smp_call_function_single()
is not trivial.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
To: davej@redhat.com
To: cpufreq@vger.kernel.org
Cc: mark.langsdorf@amd.com
---
arch/x86/kernel/cpu/cpufreq/powernow-k8.c | 128 +++++++++++++++---------------
1 file changed, 64 insertions(+), 64 deletions(-)

diff --git a/arch/x86/kernel/cpu/cpufreq/powernow-k8.c b/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
--- a/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
+++ b/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
@@ -510,41 +510,34 @@ static int core_voltage_post_transition(
return 0;
}

-static int check_supported_cpu(unsigned int cpu)
+static void check_supported_cpu(void *_rc)
{
- cpumask_t oldmask;
u32 eax, ebx, ecx, edx;
- unsigned int rc = 0;
+ int *rc = _rc;

- oldmask = current->cpus_allowed;
- set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
-
- if (smp_processor_id() != cpu) {
- printk(KERN_ERR PFX "limiting to cpu %u failed\n", cpu);
- goto out;
- }
+ *rc = -ENODEV;

if (current_cpu_data.x86_vendor != X86_VENDOR_AMD)
- goto out;
+ return;

eax = cpuid_eax(CPUID_PROCESSOR_SIGNATURE);
if (((eax & CPUID_XFAM) != CPUID_XFAM_K8) &&
((eax & CPUID_XFAM) < CPUID_XFAM_10H))
- goto out;
+ return;

if ((eax & CPUID_XFAM) == CPUID_XFAM_K8) {
if (((eax & CPUID_USE_XFAM_XMOD) != CPUID_USE_XFAM_XMOD) ||
((eax & CPUID_XMOD) > CPUID_XMOD_REV_MASK)) {
printk(KERN_INFO PFX
"Processor cpuid %x not supported\n", eax);
- goto out;
+ return;
}

eax = cpuid_eax(CPUID_GET_MAX_CAPABILITIES);
if (eax < CPUID_FREQ_VOLT_CAPABILITIES) {
printk(KERN_INFO PFX
"No frequency change capabilities detected\n");
- goto out;
+ return;
}

cpuid(CPUID_FREQ_VOLT_CAPABILITIES, &eax, &ebx, &ecx, &edx);
@@ -552,21 +545,17 @@ static int check_supported_cpu(unsigned
!= P_STATE_TRANSITION_CAPABLE) {
printk(KERN_INFO PFX
"Power state transitions not supported\n");
- goto out;
+ return;
}
} else { /* must be a HW Pstate capable processor */
cpuid(CPUID_FREQ_VOLT_CAPABILITIES, &eax, &ebx, &ecx, &edx);
if ((edx & USE_HW_PSTATE) == USE_HW_PSTATE)
cpu_family = CPU_HW_PSTATE;
else
- goto out;
+ return;
}

- rc = 1;
-
-out:
- set_cpus_allowed_ptr(current, &oldmask);
- return rc;
+ *rc = 0;
}

static int check_pst_table(struct powernow_k8_data *data, struct pst_s *pst,
@@ -1141,11 +1130,16 @@ static int transition_frequency_pstate(s
return res;
}

-/* Driver entry point to switch to the target frequency */
-static int powernowk8_target(struct cpufreq_policy *pol,
- unsigned targfreq, unsigned relation)
+struct target_data {
+ struct cpufreq_policy *pol;
+ unsigned targfreq;
+ unsigned relation;
+};
+
+static long powernowk8_target_on_cpu(void *_tdata)
{
- cpumask_t oldmask;
+ struct target_data *tdata = _tdata;
+ struct cpufreq_policy *pol = tdata->pol;
struct powernow_k8_data *data = per_cpu(powernow_data, pol->cpu);
u32 checkfid;
u32 checkvid;
@@ -1158,22 +1152,13 @@ static int powernowk8_target(struct cpuf
checkfid = data->currfid;
checkvid = data->currvid;

- /* only run on specific CPU from here on */
- oldmask = current->cpus_allowed;
- set_cpus_allowed_ptr(current, &cpumask_of_cpu(pol->cpu));
-
- if (smp_processor_id() != pol->cpu) {
- printk(KERN_ERR PFX "limiting to cpu %u failed\n", pol->cpu);
- goto err_out;
- }
-
if (pending_bit_stuck()) {
printk(KERN_ERR PFX "failing targ, change pending bit set\n");
goto err_out;
}

dprintk("targ: cpu %d, %d kHz, min %d, max %d, relation %d\n",
- pol->cpu, targfreq, pol->min, pol->max, relation);
+ pol->cpu, tdata->targfreq, pol->min, pol->max, tdata->relation);

if (query_current_values_with_pending_wait(data))
goto err_out;
@@ -1193,7 +1178,8 @@ static int powernowk8_target(struct cpuf
}

if (cpufreq_frequency_table_target(pol, data->powernow_table,
- targfreq, relation, &newstate))
+ tdata->targfreq, tdata->relation,
+ &newstate))
goto err_out;

mutex_lock(&fidvid_mutex);
@@ -1220,10 +1206,19 @@ static int powernowk8_target(struct cpuf
ret = 0;

err_out:
- set_cpus_allowed_ptr(current, &oldmask);
return ret;
}

+/* Driver entry point to switch to the target frequency */
+static int powernowk8_target(struct cpufreq_policy *pol,
+ unsigned targfreq, unsigned relation)
+{
+ struct target_data tdata = { .pol = pol,
+ .targfreq = targfreq,
+ .relation = relation };
+ return work_on_cpu(pol->cpu, powernowk8_target_on_cpu, &tdata);
+}
+
/* Driver entry point to verify the policy and range of frequencies */
static int powernowk8_verify(struct cpufreq_policy *pol)
{
@@ -1235,6 +1230,32 @@ static int powernowk8_verify(struct cpuf
return cpufreq_frequency_table_verify(pol, data->powernow_table);
}

+struct init_on_cpu {
+ struct powernow_k8_data *data;
+ int rc;
+};
+
+static void __cpuinit powernowk8_cpu_init_on_cpu(void *_init_on_cpu)
+{
+ struct init_on_cpu *init_on_cpu = _init_on_cpu;
+
+ if (pending_bit_stuck()) {
+ printk(KERN_ERR PFX "failing init, change pending bit set\n");
+ init_on_cpu->rc = -ENODEV;
+ return;
+ }
+
+ if (query_current_values_with_pending_wait(init_on_cpu->data)) {
+ init_on_cpu->rc = -ENODEV;
+ return;
+ }
+
+ if (cpu_family == CPU_OPTERON)
+ fidvid_msr_init();
+
+ init_on_cpu->rc = 0;
+}
+
static const char ACPI_PSS_BIOS_BUG_MSG[] =
KERN_ERR FW_BUG PFX "No compatible ACPI _PSS objects found.\n"
KERN_ERR FW_BUG PFX "Try again with latest BIOS.\n";
@@ -1243,13 +1264,14 @@ static const char ACPI_PSS_BIOS_BUG_MSG[
static int __cpuinit powernowk8_cpu_init(struct cpufreq_policy *pol)
{
struct powernow_k8_data *data;
- cpumask_t oldmask;
+ struct init_on_cpu init_on_cpu;
int rc;

if (!cpu_online(pol->cpu))
return -ENODEV;

- if (!check_supported_cpu(pol->cpu))
+ smp_call_function_single(pol->cpu, check_supported_cpu, &rc, 1);
+ if (rc)
return -ENODEV;

data = kzalloc(sizeof(struct powernow_k8_data), GFP_KERNEL);
@@ -1289,27 +1311,12 @@ static int __cpuinit powernowk8_cpu_init
pol->cpuinfo.transition_latency = get_transition_latency(data);

/* only run on specific CPU from here on */
- oldmask = current->cpus_allowed;
- set_cpus_allowed_ptr(current, &cpumask_of_cpu(pol->cpu));
-
- if (smp_processor_id() != pol->cpu) {
- printk(KERN_ERR PFX "limiting to cpu %u failed\n", pol->cpu);
- goto err_out_unmask;
- }
-
- if (pending_bit_stuck()) {
- printk(KERN_ERR PFX "failing init, change pending bit set\n");
- goto err_out_unmask;
- }
-
- if (query_current_values_with_pending_wait(data))
- goto err_out_unmask;
-
- if (cpu_family == CPU_OPTERON)
- fidvid_msr_init();
-
- /* run on any CPU again */
- set_cpus_allowed_ptr(current, &oldmask);
+ init_on_cpu.data = data;
+ smp_call_function_single(data->cpu, powernowk8_cpu_init_on_cpu,
+ &init_on_cpu, 1);
+ rc = init_on_cpu.rc;
+ if (rc != 0)
+ goto err_out_exit_acpi;

if (cpu_family == CPU_HW_PSTATE)
cpumask_copy(pol->cpus, cpumask_of(pol->cpu));
@@ -1346,8 +1353,7 @@ static int __cpuinit powernowk8_cpu_init

return 0;

-err_out_unmask:
- set_cpus_allowed_ptr(current, &oldmask);
+err_out_exit_acpi:
powernow_k8_cpu_exit_acpi(data);

err_out:
@@ -1372,12 +1378,20 @@ static int __devexit powernowk8_cpu_exit
return 0;
}

+static void query_values_on_cpu(void *_err)
+{
+ int *err = _err;
+ struct powernow_k8_data *data = __get_cpu_var(powernow_data);
+
+ *err = query_current_values_with_pending_wait(data);
+}
+
static unsigned int powernowk8_get(unsigned int cpu)
{
struct powernow_k8_data *data;
- cpumask_t oldmask = current->cpus_allowed;
unsigned int khz = 0;
unsigned int first;
+ int err;

first = cpumask_first(cpu_core_mask(cpu));
data = per_cpu(powernow_data, first);
@@ -1385,15 +1399,8 @@ static unsigned int powernowk8_get(unsig
if (!data)
return -EINVAL;

- set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
- if (smp_processor_id() != cpu) {
- printk(KERN_ERR PFX
- "limiting to CPU %d failed in powernowk8_get\n", cpu);
- set_cpus_allowed_ptr(current, &oldmask);
- return 0;
- }
-
- if (query_current_values_with_pending_wait(data))
+ smp_call_function_single(first, query_values_on_cpu, &err, true);
+ if (err)
goto out;

if (cpu_family == CPU_HW_PSTATE)
@@ -1404,7 +1411,6 @@ static unsigned int powernowk8_get(unsig

out:
- set_cpus_allowed_ptr(current, &oldmask);
return khz;
}

@@ -1430,7 +1436,9 @@ static int __cpuinit powernowk8_init(voi
unsigned int i, supported_cpus = 0;

for_each_online_cpu(i) {
- if (check_supported_cpu(i))
+ int rc;
+ smp_call_function_single(i, check_supported_cpu, &rc, 1);
+ if (rc == 0)
supported_cpus++;
}