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SubjectRe: [Patch] RCU trace: use scnprintf instead of snprintf
On Tue, May 12, 2009 at 06:04:15AM -0400, Amerigo Wang wrote:
>
> snprintf can return more than the size of buffer, this case
> is not expected here, obviously. Use scnprintf instead.

Good catch!!! I would welcome a simlarly careful review of the tracing
for the other RCU variants.

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

> Signed-off-by: WANG Cong <amwang@redhat.com>
> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>
> ---
> diff --git a/kernel/rcupreempt_trace.c b/kernel/rcupreempt_trace.c
> index 7c2665c..4ea4300 100644
> --- a/kernel/rcupreempt_trace.c
> +++ b/kernel/rcupreempt_trace.c
> @@ -234,11 +234,11 @@ static ssize_t rcuctrs_read(struct file *filp, char __user *buffer,
>
> mutex_lock(&rcupreempt_trace_mutex);
>
> - cnt += snprintf(&rcupreempt_trace_buf[cnt], RCUPREEMPT_TRACE_BUF_SIZE,
> + cnt += scnprintf(&rcupreempt_trace_buf[cnt], RCUPREEMPT_TRACE_BUF_SIZE,
> "CPU last cur F M\n");
> for_each_online_cpu(cpu) {
> long *flipctr = rcupreempt_flipctr(cpu);
> - cnt += snprintf(&rcupreempt_trace_buf[cnt],
> + cnt += scnprintf(&rcupreempt_trace_buf[cnt],
> RCUPREEMPT_TRACE_BUF_SIZE - cnt,
> "%3d %4ld %3ld %d %d\n",
> cpu,
> @@ -247,12 +247,12 @@ static ssize_t rcuctrs_read(struct file *filp, char __user *buffer,
> rcupreempt_flip_flag(cpu),
> rcupreempt_mb_flag(cpu));
> }
> - cnt += snprintf(&rcupreempt_trace_buf[cnt],
> + cnt += scnprintf(&rcupreempt_trace_buf[cnt],
> RCUPREEMPT_TRACE_BUF_SIZE - cnt,
> "ggp = %ld, state = %s\n",
> rcu_batches_completed(),
> rcupreempt_try_flip_state_name());
> - cnt += snprintf(&rcupreempt_trace_buf[cnt],
> + cnt += scnprintf(&rcupreempt_trace_buf[cnt],
> RCUPREEMPT_TRACE_BUF_SIZE - cnt,
> "\n");
> bcount = simple_read_from_buffer(buffer, count, ppos,


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