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Message-ID: <20131107205930.GV18245@linux.vnet.ibm.com>
Date: Thu, 7 Nov 2013 12:59:30 -0800
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Chen Gang <gang.chen@...anux.com>
Cc: josh@...edesktop.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] kernel/rcutorture.c: be sure of enough memory for
result printing
On Thu, Nov 07, 2013 at 10:30:25AM +0800, Chen Gang wrote:
> If the contents is more than 4096 bytes (e.g. if have 1K cpus), current
> sprintf() will cause memory overflow. And this fix patch is to be sure
> of memory large enough.
>
> Benefit:
>
> - do not truncate printing contents.
> - extensible, it is large enough for printing various related contents.
> - simple and clear enough for both source code readers and writers.
>
> Shortcoming:
>
> - It will waste some memory:
>
> 1 cpu now comsumes 50 - 60 bytes, and this patch provides 200 bytes.
> global printing now comsumes a few KB, and this patch provide 8KB,
> so for 1K cpus, it may waste 100 - 200 KB memory.
>
> after finish printing, it will free the related memory, quickly.
> it is a test module, so wast a little memory for extensible is OK.
>
> Related test (Fedora16 2 CPUs, 2GB RAM x86_64)
>
> - as module, with/without "torture_type=srcu".
> - build-in not boot runnable, with/without "torture_type=srcu".
> - build-in let boot runnable, with/without "torture_type=srcu".
>
>
> Signed-off-by: Chen Gang <gang.chen@...anux.com>
Thank you, queued for 3.14.
Thanx, Paul
> ---
> kernel/rcu/torture.c | 68 +++++++++++++++++++++++++------------------------
> 1 files changed, 35 insertions(+), 33 deletions(-)
>
> diff --git a/kernel/rcu/torture.c b/kernel/rcu/torture.c
> index 3929cd4..a60874c 100644
> --- a/kernel/rcu/torture.c
> +++ b/kernel/rcu/torture.c
> @@ -139,8 +139,6 @@ MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
> #define VERBOSE_PRINTK_ERRSTRING(s) \
> do { if (verbose) pr_alert("%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
>
> -static char printk_buf[4096];
> -
> static int nrealreaders;
> static struct task_struct *writer_task;
> static struct task_struct **fakewriter_tasks;
> @@ -376,7 +374,7 @@ struct rcu_torture_ops {
> void (*call)(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
> void (*cb_barrier)(void);
> void (*fqs)(void);
> - int (*stats)(char *page);
> + void (*stats)(char *page);
> int irq_capable;
> int can_boost;
> const char *name;
> @@ -578,21 +576,19 @@ static void srcu_torture_barrier(void)
> srcu_barrier(&srcu_ctl);
> }
>
> -static int srcu_torture_stats(char *page)
> +static void srcu_torture_stats(char *page)
> {
> - int cnt = 0;
> int cpu;
> int idx = srcu_ctl.completed & 0x1;
>
> - cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
> + page += sprintf(page, "%s%s per-CPU(idx=%d):",
> torture_type, TORTURE_FLAG, idx);
> for_each_possible_cpu(cpu) {
> - cnt += sprintf(&page[cnt], " %d(%lu,%lu)", cpu,
> + page += sprintf(page, " %d(%lu,%lu)", cpu,
> per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
> per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
> }
> - cnt += sprintf(&page[cnt], "\n");
> - return cnt;
> + sprintf(page, "\n");
> }
>
> static void srcu_torture_synchronize_expedited(void)
> @@ -1052,10 +1048,9 @@ rcu_torture_reader(void *arg)
> /*
> * Create an RCU-torture statistics message in the specified buffer.
> */
> -static int
> +static void
> rcu_torture_printk(char *page)
> {
> - int cnt = 0;
> int cpu;
> int i;
> long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
> @@ -1071,8 +1066,8 @@ rcu_torture_printk(char *page)
> if (pipesummary[i] != 0)
> break;
> }
> - cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG);
> - cnt += sprintf(&page[cnt],
> + page += sprintf(page, "%s%s ", torture_type, TORTURE_FLAG);
> + page += sprintf(page,
> "rtc: %p ver: %lu tfle: %d rta: %d rtaf: %d rtf: %d ",
> rcu_torture_current,
> rcu_torture_current_version,
> @@ -1080,53 +1075,52 @@ rcu_torture_printk(char *page)
> atomic_read(&n_rcu_torture_alloc),
> atomic_read(&n_rcu_torture_alloc_fail),
> atomic_read(&n_rcu_torture_free));
> - cnt += sprintf(&page[cnt], "rtmbe: %d rtbke: %ld rtbre: %ld ",
> + page += sprintf(page, "rtmbe: %d rtbke: %ld rtbre: %ld ",
> atomic_read(&n_rcu_torture_mberror),
> n_rcu_torture_boost_ktrerror,
> n_rcu_torture_boost_rterror);
> - cnt += sprintf(&page[cnt], "rtbf: %ld rtb: %ld nt: %ld ",
> + page += sprintf(page, "rtbf: %ld rtb: %ld nt: %ld ",
> n_rcu_torture_boost_failure,
> n_rcu_torture_boosts,
> n_rcu_torture_timers);
> - cnt += sprintf(&page[cnt],
> + page += sprintf(page,
> "onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
> n_online_successes, n_online_attempts,
> n_offline_successes, n_offline_attempts,
> min_online, max_online,
> min_offline, max_offline,
> sum_online, sum_offline, HZ);
> - cnt += sprintf(&page[cnt], "barrier: %ld/%ld:%ld",
> + page += sprintf(page, "barrier: %ld/%ld:%ld",
> n_barrier_successes,
> n_barrier_attempts,
> n_rcu_torture_barrier_error);
> - cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
> + page += sprintf(page, "\n%s%s ", torture_type, TORTURE_FLAG);
> if (atomic_read(&n_rcu_torture_mberror) != 0 ||
> n_rcu_torture_barrier_error != 0 ||
> n_rcu_torture_boost_ktrerror != 0 ||
> n_rcu_torture_boost_rterror != 0 ||
> n_rcu_torture_boost_failure != 0 ||
> i > 1) {
> - cnt += sprintf(&page[cnt], "!!! ");
> + page += sprintf(page, "!!! ");
> atomic_inc(&n_rcu_torture_error);
> WARN_ON_ONCE(1);
> }
> - cnt += sprintf(&page[cnt], "Reader Pipe: ");
> + page += sprintf(page, "Reader Pipe: ");
> for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
> - cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
> - cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
> - cnt += sprintf(&page[cnt], "Reader Batch: ");
> + page += sprintf(page, " %ld", pipesummary[i]);
> + page += sprintf(page, "\n%s%s ", torture_type, TORTURE_FLAG);
> + page += sprintf(page, "Reader Batch: ");
> for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
> - cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
> - cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
> - cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
> + page += sprintf(page, " %ld", batchsummary[i]);
> + page += sprintf(page, "\n%s%s ", torture_type, TORTURE_FLAG);
> + page += sprintf(page, "Free-Block Circulation: ");
> for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
> - cnt += sprintf(&page[cnt], " %d",
> + page += sprintf(page, " %d",
> atomic_read(&rcu_torture_wcount[i]));
> }
> - cnt += sprintf(&page[cnt], "\n");
> + page += sprintf(page, "\n");
> if (cur_ops->stats)
> - cnt += cur_ops->stats(&page[cnt]);
> - return cnt;
> + cur_ops->stats(page);
> }
>
> /*
> @@ -1140,10 +1134,18 @@ rcu_torture_printk(char *page)
> static void
> rcu_torture_stats_print(void)
> {
> - int cnt;
> + int size = nr_cpu_ids * 200 + 8192; /* be sure of large enough */
> + char *buf;
>
> - cnt = rcu_torture_printk(printk_buf);
> - pr_alert("%s", printk_buf);
> + buf = kmalloc(size, GFP_KERNEL);
> + if (!buf) {
> + pr_err("rcu-torture: no enough memory for printing, requre: %d",
> + size);
> + return;
> + }
> + rcu_torture_printk(buf);
> + pr_alert("%s", buf);
> + kfree(buf);
> }
>
> /*
> --
> 1.7.7.6
>
--
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