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Subject[PATCH v2] kernel/rcutorture.c: be sure of enough memory for result printing
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@asianux.com>
---
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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