Re: [PATCH] kernel/rcutorture.c: be sure of enough memory for resultprinting.
From: Chen Gang
Date: Mon Oct 21 2013 - 05:36:48 EST
BTW: I use kmalloc(), and still can pass build-in and let boot runnable
under my laptop, but I think it is not quite precise, may still need
more think of, please check (or give a confirmation whether it is OK).
Hmm... maybe the pr_err("...") also need "srcu-torture" prefix just like
another printing to let checkers easy search?
Thanks.
On 10/21/2013 02:18 PM, Chen Gang wrote:
>
> Oh, sorry, I forgot to let it pass "./scripts/checkpatch.pl", after
> finish checking, it finds a style issue (which is pointed out below), if
> necessary to send patch v2, please let me know.
>
> Thanks.
>
> On 10/21/2013 01:51 PM, 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 may waste 24KB,
>> 10 cpus may waste 96KB,
>> 100 cpus may waste 816KB,
>> 1K cpus may waste 8MB
>> ...
>> 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@xxxxxxxxxxx>
>> ---
>> kernel/rcutorture.c | 67 ++++++++++++++++++++++++++-------------------------
>> 1 files changed, 34 insertions(+), 33 deletions(-)
>>
>> diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
>> index be63101..3413bc1 100644
>> --- a/kernel/rcutorture.c
>> +++ b/kernel/rcutorture.c
>> @@ -133,8 +133,6 @@ 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;
>> @@ -370,7 +368,7 @@ 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;
>> @@ -572,21 +570,19 @@ 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)
>> @@ -1046,10 +1042,9 @@ 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 };
>> @@ -1065,8 +1060,8 @@ 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,
>> @@ -1074,53 +1069,52 @@ 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);
>
> Oh, sorry, this line has a waste white space.
>
>> }
>>
>> /*
>> @@ -1134,10 +1128,17 @@ rcu_torture_printk(char *page)
>> static void
>> rcu_torture_stats_print(void)
>> {
>> - int cnt;
>> + int size = (nr_cpu_ids + 2) * PAGE_SIZE; /* 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("no enough memory for printing, requre: %d", size);
>> + return;
>> + }
>> + rcu_torture_printk(buf);
>> + pr_alert("%s", buf);
>> + kfree(buf);
>> }
>>
>> /*
>>
>
>
--
Chen Gang
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