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authorLi Zefan <lizf@cn.fujitsu.com>2009-12-30 14:23:40 +0800
committerIngo Molnar <mingo@elte.hu>2009-12-30 07:50:49 +0100
commite6d9491bf8ba6728cc86aeabbc688d20ec0563b5 (patch)
tree1ca34f9f0608f688069da43688b2a9b8fa163644 /kernel
parent3d13ec2efdb5843ad91e57b60d50b44d922cf063 (diff)
downloadvexpress-lsk-e6d9491bf8ba6728cc86aeabbc688d20ec0563b5.tar.gz
ksym_tracer: Fix race when incrementing count
We are under rcu read section but not holding the write lock, so count++ is not atomic. Use atomic64_t instead. 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: <4B3AF1EC.9010608@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace_ksym.c12
1 files changed, 7 insertions, 5 deletions
diff --git a/kernel/trace/trace_ksym.c b/kernel/trace/trace_ksym.c
index 160a8d8b37a..67d79f709fc 100644
--- a/kernel/trace/trace_ksym.c
+++ b/kernel/trace/trace_ksym.c
@@ -32,6 +32,8 @@
#include <linux/hw_breakpoint.h>
#include <asm/hw_breakpoint.h>
+#include <asm/atomic.h>
+
/*
* For now, let us restrict the no. of symbols traced simultaneously to number
* of available hardware breakpoint registers.
@@ -44,7 +46,7 @@ struct trace_ksym {
struct perf_event **ksym_hbp;
struct perf_event_attr attr;
#ifdef CONFIG_PROFILE_KSYM_TRACER
- unsigned long counter;
+ atomic64_t counter;
#endif
struct hlist_node ksym_hlist;
};
@@ -69,9 +71,8 @@ void ksym_collect_stats(unsigned long hbp_hit_addr)
rcu_read_lock();
hlist_for_each_entry_rcu(entry, node, &ksym_filter_head, ksym_hlist) {
- if ((entry->attr.bp_addr == hbp_hit_addr) &&
- (entry->counter <= MAX_UL_INT)) {
- entry->counter++;
+ if (entry->attr.bp_addr == hbp_hit_addr) {
+ atomic64_inc(&entry->counter);
break;
}
}
@@ -501,7 +502,8 @@ static int ksym_tracer_stat_show(struct seq_file *m, void *v)
seq_printf(m, " %-36s", fn_name);
else
seq_printf(m, " %-36s", "<NA>");
- seq_printf(m, " %15lu\n", entry->counter);
+ seq_printf(m, " %15llu\n",
+ (unsigned long long)atomic64_read(&entry->counter));
return 0;
}