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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>
This commit is contained in:
Li Zefan 2009-12-30 14:23:40 +08:00 committed by Ingo Molnar
parent 3d13ec2efd
commit e6d9491bf8
1 changed files with 7 additions and 5 deletions
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12
kernel/trace/trace_ksym.c
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@ -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;
}