sparc/sysfs: Replace racy task affinity logic (ea875ec9) · Commits · 戴 / test

The mmustat_enable sysfs file accessor functions must run code 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. concurrent affinity settings for that thread resulting in code executing on the wrong CPU and overwriting the new affinity setting. Replace it by using work_on_cpu() which guarantees to run the code on the requested CPU. Protection against CPU hotplug is not required as the open sysfs file already prevents the removal from the CPU offline callback. Using the hotplug protected version would actually be wrong because it would deadlock against a CPU hotplug operation of the CPU associated to the sysfs file in progress. Signed-off-by:

Thomas Gleixner <tglx@linutronix.de> Acked-by:

David S. Miller <davem@davemloft.net> Cc: fenghua.yu@intel.com Cc: tony.luck@intel.com Cc: herbert@gondor.apana.org.au Cc: rjw@rjwysocki.net Cc: peterz@infradead.org Cc: benh@kernel.crashing.org Cc: bigeasy@linutronix.de Cc: jiangshanlai@gmail.com Cc: sparclinux@vger.kernel.org Cc: viresh.kumar@linaro.org Cc: mpe@ellerman.id.au Cc: tj@kernel.org Cc: lenb@kernel.org Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1704131001270.2408@nanos Signed-off-by:

Thomas Gleixner <tglx@linutronix.de>

arch/sparc/kernel/sysfs.c

+11 −28

Original line number	Diff line number	Diff line
		@@ -98,27 +98,7 @@ static struct attribute_group mmu_stat_group = {
		.name = "mmu_stats",
		};

		/* XXX convert to rusty's on_one_cpu */
		static unsigned long run_on_cpu(unsigned long cpu,
		unsigned long (*func)(unsigned long),
		unsigned long arg)
		{
		cpumask_t old_affinity;
		unsigned long ret;

		cpumask_copy(&old_affinity, &current->cpus_allowed);
		/* should return -EINVAL to userspace */
		if (set_cpus_allowed_ptr(current, cpumask_of(cpu)))
		return 0;

		ret = func(arg);

		set_cpus_allowed_ptr(current, &old_affinity);

		return ret;
		}

		static unsigned long read_mmustat_enable(unsigned long junk)
		static long read_mmustat_enable(void *data __maybe_unused)
		{
		unsigned long ra = 0;

		@@ -127,11 +107,11 @@ static unsigned long read_mmustat_enable(unsigned long junk)
		return ra != 0;
		}

		static unsigned long write_mmustat_enable(unsigned long val)
		static long write_mmustat_enable(void *data)
		{
		unsigned long ra, orig_ra;
		unsigned long ra, orig_ra, *val = data;

		if (val)
		if (*val)
		ra = __pa(&per_cpu(mmu_stats, smp_processor_id()));
		else
		ra = 0UL;
		@@ -142,7 +122,8 @@ static unsigned long write_mmustat_enable(unsigned long val)
		static ssize_t show_mmustat_enable(struct device *s,
		struct device_attribute attr, char buf)
		{
		unsigned long val = run_on_cpu(s->id, read_mmustat_enable, 0);
		long val = work_on_cpu(s->id, read_mmustat_enable, NULL);

		return sprintf(buf, "%lx\n", val);
		}

		@@ -150,13 +131,15 @@ static ssize_t store_mmustat_enable(struct device *s,
		struct device_attribute attr, const char buf,
		size_t count)
		{
		unsigned long val, err;
		int ret = sscanf(buf, "%lu", &val);
		unsigned long val;
		long err;
		int ret;

		ret = sscanf(buf, "%lu", &val);
		if (ret != 1)
		return -EINVAL;

		err = run_on_cpu(s->id, write_mmustat_enable, val);
		err = work_on_cpu(s->id, write_mmustat_enable, &val);
		if (err)
		return -EIO;

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