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Commit e6d9491b authored by Li Zefan's avatar Li Zefan Committed by Ingo Molnar
Browse files

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: default avatarLi 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: default avatarIngo Molnar <mingo@elte.hu>
parent 3d13ec2e

kernel/trace/trace_ksym.c

+7 −5
Original line number Diff line number Diff line
@@ -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;

}