Commit 9fe24c4e authored by Thomas Gleixner's avatar Thomas Gleixner

cpufreq/sparc-us3: Replace racy task affinity logic

The access to the safari config register in the CPU frequency functions
must be executed on the target CPU. This is achieved by temporarily setting
the affinity of the calling user space thread to the requested CPU and
reset it to the original affinity afterwards.

That's racy vs. CPU hotplug and concurrent affinity settings for that
thread resulting in code executing on the wrong CPU and overwriting the
new affinity setting.

Replace it by a straight forward smp function call. 
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: linux-pm@vger.kernel.org
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Len Brown <lenb@kernel.org>
Link: http://lkml.kernel.org/r/20170412201043.047558840@linutronix.deSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 205dcc1e
...@@ -35,22 +35,28 @@ static struct us3_freq_percpu_info *us3_freq_table; ...@@ -35,22 +35,28 @@ static struct us3_freq_percpu_info *us3_freq_table;
#define SAFARI_CFG_DIV_32 0x0000000080000000UL #define SAFARI_CFG_DIV_32 0x0000000080000000UL
#define SAFARI_CFG_DIV_MASK 0x00000000C0000000UL #define SAFARI_CFG_DIV_MASK 0x00000000C0000000UL
static unsigned long read_safari_cfg(void) static void read_safari_cfg(void *arg)
{ {
unsigned long ret; unsigned long ret, *val = arg;
__asm__ __volatile__("ldxa [%%g0] %1, %0" __asm__ __volatile__("ldxa [%%g0] %1, %0"
: "=&r" (ret) : "=&r" (ret)
: "i" (ASI_SAFARI_CONFIG)); : "i" (ASI_SAFARI_CONFIG));
return ret; *val = ret;
} }
static void write_safari_cfg(unsigned long val) static void update_safari_cfg(void *arg)
{ {
unsigned long reg, *new_bits = arg;
read_safari_cfg(&reg);
reg &= ~SAFARI_CFG_DIV_MASK;
reg |= *new_bits;
__asm__ __volatile__("stxa %0, [%%g0] %1\n\t" __asm__ __volatile__("stxa %0, [%%g0] %1\n\t"
"membar #Sync" "membar #Sync"
: /* no outputs */ : /* no outputs */
: "r" (val), "i" (ASI_SAFARI_CONFIG) : "r" (reg), "i" (ASI_SAFARI_CONFIG)
: "memory"); : "memory");
} }
...@@ -78,29 +84,17 @@ static unsigned long get_current_freq(unsigned int cpu, unsigned long safari_cfg ...@@ -78,29 +84,17 @@ static unsigned long get_current_freq(unsigned int cpu, unsigned long safari_cfg
static unsigned int us3_freq_get(unsigned int cpu) static unsigned int us3_freq_get(unsigned int cpu)
{ {
cpumask_t cpus_allowed;
unsigned long reg; unsigned long reg;
unsigned int ret;
cpumask_copy(&cpus_allowed, &current->cpus_allowed);
set_cpus_allowed_ptr(current, cpumask_of(cpu));
reg = read_safari_cfg();
ret = get_current_freq(cpu, reg);
set_cpus_allowed_ptr(current, &cpus_allowed);
return ret; if (smp_call_function_single(cpu, read_safari_cfg, &reg, 1))
return 0;
return get_current_freq(cpu, reg);
} }
static int us3_freq_target(struct cpufreq_policy *policy, unsigned int index) static int us3_freq_target(struct cpufreq_policy *policy, unsigned int index)
{ {
unsigned int cpu = policy->cpu; unsigned int cpu = policy->cpu;
unsigned long new_bits, new_freq, reg; unsigned long new_bits, new_freq;
cpumask_t cpus_allowed;
cpumask_copy(&cpus_allowed, &current->cpus_allowed);
set_cpus_allowed_ptr(current, cpumask_of(cpu));
new_freq = sparc64_get_clock_tick(cpu) / 1000; new_freq = sparc64_get_clock_tick(cpu) / 1000;
switch (index) { switch (index) {
...@@ -121,15 +115,7 @@ static int us3_freq_target(struct cpufreq_policy *policy, unsigned int index) ...@@ -121,15 +115,7 @@ static int us3_freq_target(struct cpufreq_policy *policy, unsigned int index)
BUG(); BUG();
} }
reg = read_safari_cfg(); return smp_call_function_single(cpu, update_safari_cfg, &new_bits, 1);
reg &= ~SAFARI_CFG_DIV_MASK;
reg |= new_bits;
write_safari_cfg(reg);
set_cpus_allowed_ptr(current, &cpus_allowed);
return 0;
} }
static int __init us3_freq_cpu_init(struct cpufreq_policy *policy) static int __init us3_freq_cpu_init(struct cpufreq_policy *policy)
......
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