ksym_tracer: Fix to make the tracer work

ksym tracer doesn't work:

 # echo tasklist_lock:rw- > ksym_trace_filter
 -bash: echo: write error: No such device

It's because we pass to perf_event_create_kernel_counter()
a cpu number which is not present.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4B3AF19E.1010201@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 7 insertions, 4 deletions

diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c
index 366eedf949c0..48fb0bb6992a 100644
--- a/kernel/hw_breakpoint.c
+++ b/kernel/hw_breakpoint.c
@@ -40,6 +40,7 @@
 #include <linux/percpu.h>
 #include <linux/sched.h>
 #include <linux/init.h>
+#include <linux/cpu.h>
 #include <linux/smp.h>
 
 #include <linux/hw_breakpoint.h>
@@ -388,7 +389,8 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
         if (!cpu_events)
                 return ERR_PTR(-ENOMEM);
 
-        for_each_possible_cpu(cpu) {
+        get_online_cpus();
+        for_each_online_cpu(cpu) {
                 pevent = per_cpu_ptr(cpu_events, cpu);
                 bp = perf_event_create_kernel_counter(attr, cpu, -1, triggered);
 
@@ -399,18 +401,20 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
                         goto fail;
                 }
         }
+        put_online_cpus();
 
         return cpu_events;
 
 fail:
-        for_each_possible_cpu(cpu) {
+        for_each_online_cpu(cpu) {
                 pevent = per_cpu_ptr(cpu_events, cpu);
                 if (IS_ERR(*pevent))
                         break;
                 unregister_hw_breakpoint(*pevent);
         }
+        put_online_cpus();
+
         free_percpu(cpu_events);
-        /* return the error if any */
         return ERR_PTR(err);
 }
 EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
diff --git a/kernel/trace/trace_ksym.c b/kernel/trace/trace_ksym.c
index faf37fa4408c..340b6ff193e0 100644
--- a/kernel/trace/trace_ksym.c
+++ b/kernel/trace/trace_ksym.c
@@ -197,7 +197,6 @@ int process_new_ksym_entry(char *ksymname, int op, unsigned long addr)
         entry->attr.bp_addr = addr;
         entry->attr.bp_len = HW_BREAKPOINT_LEN_4;
 
-        ret = -EAGAIN;
         entry->ksym_hbp = register_wide_hw_breakpoint(&entry->attr,
                                         ksym_hbp_handler);