percpu: Add __percpu sparse annotations to hw_breakpoint

Add __percpu sparse annotations to hw_breakpoint.

These annotations are to make sparse consider percpu variables to be
in a different address space and warn if accessed without going
through percpu accessors.  This patch doesn't affect normal builds.

In kernel/hw_breakpoint.c, per_cpu(nr_task_bp_pinned, cpu)'s will
trigger spurious noderef related warnings from sparse.  Changing it to
&per_cpu(nr_task_bp_pinned[0], cpu) will work around the problem but
deemed to ugly by the maintainer.  Leave it alone until better
solution can be found.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
LKML-Reference: <4B7B4B7A.9050902@kernel.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h
index 5977b72..c70d27a 100644 (file)
--- a/include/linux/hw_breakpoint.h
+++ b/include/linux/hw_breakpoint.h
@@ -66,14 +66,14 @@ register_wide_hw_breakpoint_cpu(struct perf_event_attr *attr,
                                perf_overflow_handler_t triggered,
                                int cpu);
 
-extern struct perf_event **
+extern struct perf_event * __percpu *
 register_wide_hw_breakpoint(struct perf_event_attr *attr,
                            perf_overflow_handler_t triggered);
 
 extern int register_perf_hw_breakpoint(struct perf_event *bp);
 extern int __register_perf_hw_breakpoint(struct perf_event *bp);
 extern void unregister_hw_breakpoint(struct perf_event *bp);
-extern void unregister_wide_hw_breakpoint(struct perf_event **cpu_events);
+extern void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events);
 
 extern int dbg_reserve_bp_slot(struct perf_event *bp);
 extern int dbg_release_bp_slot(struct perf_event *bp);
@@ -100,7 +100,7 @@ static inline struct perf_event *
 register_wide_hw_breakpoint_cpu(struct perf_event_attr *attr,
                                perf_overflow_handler_t  triggered,
                                int cpu)                { return NULL; }
-static inline struct perf_event **
+static inline struct perf_event * __percpu *
 register_wide_hw_breakpoint(struct perf_event_attr *attr,
                            perf_overflow_handler_t triggered)  { return NULL; }
 static inline int
@@ -109,7 +109,7 @@ static inline int
 __register_perf_hw_breakpoint(struct perf_event *bp)   { return -ENOSYS; }
 static inline void unregister_hw_breakpoint(struct perf_event *bp)     { }
 static inline void
-unregister_wide_hw_breakpoint(struct perf_event **cpu_events)          { }
+unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)        { }
 static inline int
 reserve_bp_slot(struct perf_event *bp)                 {return -ENOSYS; }
 static inline void release_bp_slot(struct perf_event *bp)              { }

diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c
index 967e661..6542eac 100644 (file)
--- a/kernel/hw_breakpoint.c
+++ b/kernel/hw_breakpoint.c
@@ -413,17 +413,17 @@ EXPORT_SYMBOL_GPL(unregister_hw_breakpoint);
  *
  * @return a set of per_cpu pointers to perf events
  */
-struct perf_event **
+struct perf_event * __percpu *
 register_wide_hw_breakpoint(struct perf_event_attr *attr,
                            perf_overflow_handler_t triggered)
 {
-       struct perf_event **cpu_events, **pevent, *bp;
+       struct perf_event * __percpu *cpu_events, **pevent, *bp;
        long err;
        int cpu;
 
        cpu_events = alloc_percpu(typeof(*cpu_events));
        if (!cpu_events)
-               return ERR_PTR(-ENOMEM);
+               return (void __percpu __force *)ERR_PTR(-ENOMEM);
 
        get_online_cpus();
        for_each_online_cpu(cpu) {
@@ -451,7 +451,7 @@ fail:
        put_online_cpus();
 
        free_percpu(cpu_events);
-       return ERR_PTR(err);
+       return (void __percpu __force *)ERR_PTR(err);
 }
 EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
 
@@ -459,7 +459,7 @@ EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
  * unregister_wide_hw_breakpoint - unregister a wide breakpoint in the kernel
  * @cpu_events: the per cpu set of events to unregister
  */
-void unregister_wide_hw_breakpoint(struct perf_event **cpu_events)
+void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)
 {
        int cpu;
        struct perf_event **pevent;

diff --git a/samples/hw_breakpoint/data_breakpoint.c b/samples/hw_breakpoint/data_breakpoint.c
index c69cbe9..bd0f337 100644 (file)
--- a/samples/hw_breakpoint/data_breakpoint.c
+++ b/samples/hw_breakpoint/data_breakpoint.c
@@ -34,7 +34,7 @@
 #include <linux/perf_event.h>
 #include <linux/hw_breakpoint.h>
 
-struct perf_event **sample_hbp;
+struct perf_event * __percpu *sample_hbp;
 
 static char ksym_name[KSYM_NAME_LEN] = "pid_max";
 module_param_string(ksym, ksym_name, KSYM_NAME_LEN, S_IRUGO);
@@ -61,8 +61,8 @@ static int __init hw_break_module_init(void)
        attr.bp_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
 
        sample_hbp = register_wide_hw_breakpoint(&attr, sample_hbp_handler);
-       if (IS_ERR(sample_hbp)) {
-               ret = PTR_ERR(sample_hbp);
+       if (IS_ERR((void __force *)sample_hbp)) {
+               ret = PTR_ERR((void __force *)sample_hbp);
                goto fail;
        }