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Subject[PATCH 2/6] sched: add function to execute a function synchronously on a physical cpu
Date
On some hardware models (e.g. Dell Studio 1555 laptop) some hardware
related functions (e.g. SMIs) are to be executed on physical cpu 0
only. Instead of open coding such a functionality multiple times in
the kernel add a service function for this purpose. This will enable
the possibility to take special measures in virtualized environments
like Xen, too.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
include/linux/sched.h | 9 +++++++++
kernel/sched/core.c | 26 ++++++++++++++++++++++++++
2 files changed, 35 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index a10494a..dfadf1a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2247,6 +2247,7 @@ extern void do_set_cpus_allowed(struct task_struct *p,

extern int set_cpus_allowed_ptr(struct task_struct *p,
const struct cpumask *new_mask);
+int call_sync_on_phys_cpu(unsigned cpu, int (*func)(void *), void *par);
#else
static inline void do_set_cpus_allowed(struct task_struct *p,
const struct cpumask *new_mask)
@@ -2259,6 +2260,14 @@ static inline int set_cpus_allowed_ptr(struct task_struct *p,
return -EINVAL;
return 0;
}
+static inline int call_sync_on_phys_cpu(unsigned cpu, int (*func)(void *),
+ void *par)
+{
+ if (cpu != 0)
+ return -EINVAL;
+
+ return func(par);
+}
#endif

#ifdef CONFIG_NO_HZ_COMMON
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 41f6b22..cb9955f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1265,6 +1265,32 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
}
EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);

+int call_sync_on_phys_cpu(unsigned cpu, int (*func)(void *), void *par)
+{
+ cpumask_var_t old_mask;
+ int ret;
+
+ if (cpu >= nr_cpu_ids)
+ return -EINVAL;
+
+ if (!alloc_cpumask_var(&old_mask, GFP_KERNEL))
+ return -ENOMEM;
+
+ cpumask_copy(old_mask, &current->cpus_allowed);
+ ret = set_cpus_allowed_ptr(current, cpumask_of(cpu));
+ if (ret)
+ goto out;
+
+ ret = func(par);
+
+ set_cpus_allowed_ptr(current, old_mask);
+
+out:
+ free_cpumask_var(old_mask);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(call_sync_on_phys_cpu);
+
void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
{
#ifdef CONFIG_SCHED_DEBUG
--
2.6.2
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