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Subject[PATCH rcu 05/17] refscale: Prevent buffer to pr_alert() being too long
Date
From: Li Zhijian <lizhijian@cn.fujitsu.com>

0Day/LKP observed that the refscale results fail to complete when larger
values of nrun (such as 300) are specified. The problem is that printk()
can accept at most a 1024-byte buffer. This commit therefore prints
the buffer whenever its length exceeds 800 bytes.

CC: Philip Li <philip.li@intel.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/refscale.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index b59457cef88d5..d8ed1ca3adc04 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -604,7 +604,7 @@ static u64 process_durations(int n)
char *buf;
u64 sum = 0;

- buf = kmalloc(128 + nreaders * 32, GFP_KERNEL);
+ buf = kmalloc(800 + 64, GFP_KERNEL);
if (!buf)
return 0;
buf[0] = 0;
@@ -617,13 +617,15 @@ static u64 process_durations(int n)

if (i % 5 == 0)
strcat(buf, "\n");
+ if (strlen(buf) >= 800) {
+ pr_alert("%s", buf);
+ buf[0] = 0;
+ }
strcat(buf, buf1);

sum += rt->last_duration_ns;
}
- strcat(buf, "\n");
-
- SCALEOUT("%s\n", buf);
+ pr_alert("%s\n", buf);

kfree(buf);
return sum;
@@ -647,7 +649,7 @@ static int main_func(void *arg)

VERBOSE_SCALEOUT("main_func task started");
result_avg = kzalloc(nruns * sizeof(*result_avg), GFP_KERNEL);
- buf = kzalloc(64 + nruns * 32, GFP_KERNEL);
+ buf = kzalloc(800 + 64, GFP_KERNEL);
if (!result_avg || !buf) {
VERBOSE_SCALEOUT_ERRSTRING("out of memory");
goto oom_exit;
@@ -695,10 +697,7 @@ static int main_func(void *arg)
// Print the average of all experiments
SCALEOUT("END OF TEST. Calculating average duration per loop (nanoseconds)...\n");

- buf[0] = 0;
- strcat(buf, "\n");
- strcat(buf, "Runs\tTime(ns)\n");
-
+ pr_alert("Runs\tTime(ns)\n");
for (exp = 0; exp < nruns; exp++) {
u64 avg;
u32 rem;
@@ -706,9 +705,13 @@ static int main_func(void *arg)
avg = div_u64_rem(result_avg[exp], 1000, &rem);
sprintf(buf1, "%d\t%llu.%03u\n", exp + 1, avg, rem);
strcat(buf, buf1);
+ if (strlen(buf) >= 800) {
+ pr_alert("%s", buf);
+ buf[0] = 0;
+ }
}

- SCALEOUT("%s", buf);
+ pr_alert("%s", buf);

oom_exit:
// This will shutdown everything including us.
--
2.31.1.189.g2e36527f23
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