forked from luck/tmp_suning_uos_patched
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>
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@ -32,6 +32,8 @@
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#include <linux/hw_breakpoint.h>
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#include <asm/hw_breakpoint.h>
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#include <asm/atomic.h>
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/*
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* For now, let us restrict the no. of symbols traced simultaneously to number
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* of available hardware breakpoint registers.
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@ -44,7 +46,7 @@ struct trace_ksym {
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struct perf_event **ksym_hbp;
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struct perf_event_attr attr;
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#ifdef CONFIG_PROFILE_KSYM_TRACER
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unsigned long counter;
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atomic64_t counter;
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#endif
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struct hlist_node ksym_hlist;
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};
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@ -69,9 +71,8 @@ void ksym_collect_stats(unsigned long hbp_hit_addr)
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rcu_read_lock();
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hlist_for_each_entry_rcu(entry, node, &ksym_filter_head, ksym_hlist) {
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if ((entry->attr.bp_addr == hbp_hit_addr) &&
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(entry->counter <= MAX_UL_INT)) {
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entry->counter++;
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if (entry->attr.bp_addr == hbp_hit_addr) {
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atomic64_inc(&entry->counter);
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break;
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}
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}
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@ -501,7 +502,8 @@ static int ksym_tracer_stat_show(struct seq_file *m, void *v)
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seq_printf(m, " %-36s", fn_name);
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else
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seq_printf(m, " %-36s", "<NA>");
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seq_printf(m, " %15lu\n", entry->counter);
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seq_printf(m, " %15llu\n",
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(unsigned long long)atomic64_read(&entry->counter));
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return 0;
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}
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