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Date: Fri, 20 Jun 2014 15:04:31 -0700
From: Joe Perches <joe@...ches.com>
To: paulmck@...ux.vnet.ibm.com
Cc: Pranith Kumar <bobby.prani@...il.com>,
LKML <linux-kernel@...r.kernel.org>, romanov.arya@...il.com,
Josh Triplett <josh@...htriplett.org>
Subject: Re: [RFC PATCH] use snprintf instead of sprintf in
rcu_torture_printk
On Thu, 2014-06-19 at 21:54 -0700, Paul E. McKenney wrote:
> On Thu, Jun 19, 2014 at 08:13:22PM -0400, Pranith Kumar wrote:
> > On 06/19/2014 07:49 PM, Paul E. McKenney wrote:
> > > On Thu, Jun 19, 2014 at 07:24:48PM -0400, Pranith Kumar wrote:
> > >> (dropping some CCs)
> > >>
> > >> On 06/19/2014 05:00 PM, Paul E. McKenney wrote:
> > >>> On Wed, Jun 18, 2014 at 12:49:42PM -0700, Joe Perches wrote:
> > >>>>
> > >>>> I believe the function doesn't work well.
> > >>>>
> > >>>> static void
> > >>>> rcu_torture_stats_print(void)
> > >>>> {
> > >>>> int size = nr_cpu_ids * 200 + 8192;
> > >>>> char *buf;
> > >>>>
> > >>>> buf = kmalloc(size, GFP_KERNEL);
> > >>>> if (!buf) {
> > >>>> pr_err("rcu-torture: Out of memory, need: %d\n", size);
> > >>>> return;
> > >>>> }
> > >>>> rcu_torture_printk(buf);
> > >>>> pr_alert("%s", buf);
> > >>>> kfree(buf);
> > >>>> }
> > >>>>
> > >>>> rcu_torture_printk simply fills buf
> > >>>>
> > >>>> btw: I believe the arguments should pass size and
> > >>>> rcu_torture_printk should use snprintf/size
> > >>>>
> > >>>> but all printks are limited to a maximum of 1024
> > >>>> bytes so the large allocation is senseless and
> > >>>> would even if it worked, would likely need to be
> > >>>> vmalloc/vfree
> > >>>
> > >>> Fair point!
> > >>>
> > >>> Pranith, Romanov, if you would like part of RCU that is less touchy
> > >>> about random hacking, this would be a good place to start. Scripts in
> > >>> tools/testing/selftests/rcutorture/bin do care about some of the format,
> > >>> but the variable-length portion generated by cur_ops->stats() is as far
> > >>> as I know only parsed by human eyes.
> > >>>
> > >>
> > >> Here is a first run of the change. Please let me know if I am totally off. RFC. :)
> > >
> > > Thank you for taking this on!
> >
> > You are most welcome :)
> >
> > >
> > >> Three things on Todo list:
> > >>
> > >> * We need to check that we are using less than the allocated size of the buffer (used > size). (we are allocating a big buffer, so not sure if necessary)
> > >> * Need to check with the scripts if they are working.
> > >> * I used a loop for pr_alert(). I am not sure this is right, there should be a better way for printing large buffers
> > >>
> > >> If the overall structure is ok I will go ahead and check how the scripts are handling these changes.
> > >
> > > One other thing... Convince this function (and a few others that it
> > > calls) that the system really has 4096 CPUs, run this code, and see wshat
> > > actually happens both before and after. Just to get a bit of practice
> > > mixed in with the theory. ;-)
> > >
> >
> > OK. I think to do this I need to use 4096 instead of nr_cpu_ids. I will try this and see how it goes :)
>
> That's the spirit! You will probably have to adjust a few other things
> as well.
Perhaps this should not use the allocation / page buffer
and instead call pr_alert and pr_cont directly like this:
include/linux/torture.h | 2 +-
kernel/rcu/rcutorture.c | 110 +++++++++++++++++++++++-------------------------
kernel/torture.c | 16 +++----
3 files changed, 60 insertions(+), 68 deletions(-)
diff --git a/include/linux/torture.h b/include/linux/torture.h
index 5ca58fc..fec46f8 100644
--- a/include/linux/torture.h
+++ b/include/linux/torture.h
@@ -51,7 +51,7 @@
/* Definitions for online/offline exerciser. */
int torture_onoff_init(long ooholdoff, long oointerval);
-char *torture_onoff_stats(char *page);
+void torture_onoff_stats(void);
bool torture_onoff_failures(void);
/* Low-rider random number generator. */
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 7fa34f8..bb6db08 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -242,7 +242,7 @@ struct rcu_torture_ops {
void (*call)(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
void (*cb_barrier)(void);
void (*fqs)(void);
- void (*stats)(char *page);
+ void (*stats)(void);
int irq_capable;
int can_boost;
const char *name;
@@ -525,21 +525,21 @@ static void srcu_torture_barrier(void)
srcu_barrier(&srcu_ctl);
}
-static void srcu_torture_stats(char *page)
+static void srcu_torture_stats(void)
{
int cpu;
int idx = srcu_ctl.completed & 0x1;
- page += sprintf(page, "%s%s per-CPU(idx=%d):",
- torture_type, TORTURE_FLAG, idx);
+ pr_alert("%s%s per-CPU(idx=%d):",
+ torture_type, TORTURE_FLAG, idx);
for_each_possible_cpu(cpu) {
long c0, c1;
c0 = (long)per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx];
c1 = (long)per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx];
- page += sprintf(page, " %d(%ld,%ld)", cpu, c0, c1);
+ pr_cont(" %d(%ld,%ld)", cpu, c0, c1);
}
- sprintf(page, "\n");
+ pr_cont("\n");
}
static void srcu_torture_synchronize_expedited(void)
@@ -1031,10 +1031,10 @@ rcu_torture_reader(void *arg)
}
/*
- * Create an RCU-torture statistics message in the specified buffer.
+ * Print RCU-torture statistics
*/
static void
-rcu_torture_printk(char *page)
+rcu_torture_printk(void)
{
int cpu;
int i;
@@ -1052,55 +1052,60 @@ rcu_torture_printk(char *page)
if (pipesummary[i] != 0)
break;
}
- 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,
- list_empty(&rcu_torture_freelist),
- atomic_read(&n_rcu_torture_alloc),
- atomic_read(&n_rcu_torture_alloc_fail),
- atomic_read(&n_rcu_torture_free));
- 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);
- page += sprintf(page, "rtbf: %ld rtb: %ld nt: %ld ",
- n_rcu_torture_boost_failure,
- n_rcu_torture_boosts,
- n_rcu_torture_timers);
- page = torture_onoff_stats(page);
- page += sprintf(page, "barrier: %ld/%ld:%ld",
- n_barrier_successes,
- n_barrier_attempts,
- n_rcu_torture_barrier_error);
- page += sprintf(page, "\n%s%s ", torture_type, TORTURE_FLAG);
+
+ pr_alert("%s%s ", torture_type, TORTURE_FLAG);
+ pr_cont("rtc: %p ver: %lu tfle: %d rta: %d rtaf: %d rtf: %d ",
+ rcu_torture_current,
+ rcu_torture_current_version,
+ list_empty(&rcu_torture_freelist),
+ atomic_read(&n_rcu_torture_alloc),
+ atomic_read(&n_rcu_torture_alloc_fail),
+ atomic_read(&n_rcu_torture_free));
+ pr_cont("rtmbe: %d rtbke: %ld rtbre: %ld ",
+ atomic_read(&n_rcu_torture_mberror),
+ n_rcu_torture_boost_ktrerror,
+ n_rcu_torture_boost_rterror);
+ pr_cont("rtbf: %ld rtb: %ld nt: %ld ",
+ n_rcu_torture_boost_failure,
+ n_rcu_torture_boosts,
+ n_rcu_torture_timers);
+ torture_onoff_stats();
+ pr_cont("barrier: %ld/%ld:%ld\n",
+ n_barrier_successes,
+ n_barrier_attempts,
+ n_rcu_torture_barrier_error);
+
+ pr_alert("%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) {
- page += sprintf(page, "!!! ");
+ pr_cont("%s", "!!! ");
atomic_inc(&n_rcu_torture_error);
WARN_ON_ONCE(1);
}
- page += sprintf(page, "Reader Pipe: ");
+ pr_cont("Reader Pipe: ");
for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
- page += sprintf(page, " %ld", pipesummary[i]);
- page += sprintf(page, "\n%s%s ", torture_type, TORTURE_FLAG);
- page += sprintf(page, "Reader Batch: ");
+ pr_cont(" %ld", pipesummary[i]);
+ pr_cont("\n");
+
+ pr_alert("%s%s ", torture_type, TORTURE_FLAG);
+ pr_cont("Reader Batch: ");
for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
- page += sprintf(page, " %ld", batchsummary[i]);
- page += sprintf(page, "\n%s%s ", torture_type, TORTURE_FLAG);
- page += sprintf(page, "Free-Block Circulation: ");
+ pr_cont(" %ld", batchsummary[i]);
+ pr_cont("\n");
+
+ pr_alert("%s%s ", torture_type, TORTURE_FLAG);
+ pr_cont("Free-Block Circulation: ");
for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
- page += sprintf(page, " %d",
- atomic_read(&rcu_torture_wcount[i]));
+ pr_cont(" %d", atomic_read(&rcu_torture_wcount[i]));
}
- page += sprintf(page, "\n");
+ pr_cont("\n");
+
if (cur_ops->stats)
- cur_ops->stats(page);
+ cur_ops->stats();
if (rtcv_snap == rcu_torture_current_version &&
rcu_torture_current != NULL) {
int __maybe_unused flags;
@@ -1109,10 +1114,9 @@ rcu_torture_printk(char *page)
rcutorture_get_gp_data(cur_ops->ttype,
&flags, &gpnum, &completed);
- page += sprintf(page,
- "??? Writer stall state %d g%lu c%lu f%#x\n",
- rcu_torture_writer_state,
- gpnum, completed, flags);
+ pr_alert("??? Writer stall state %d g%lu c%lu f%#x\n",
+ rcu_torture_writer_state,
+ gpnum, completed, flags);
show_rcu_gp_kthreads();
rcutorture_trace_dump();
}
@@ -1130,17 +1134,7 @@ rcu_torture_printk(char *page)
static void
rcu_torture_stats_print(void)
{
- int size = nr_cpu_ids * 200 + 8192;
- char *buf;
-
- buf = kmalloc(size, GFP_KERNEL);
- if (!buf) {
- pr_err("rcu-torture: Out of memory, need: %d", size);
- return;
- }
- rcu_torture_printk(buf);
- pr_alert("%s", buf);
- kfree(buf);
+ rcu_torture_printk();
}
/*
diff --git a/kernel/torture.c b/kernel/torture.c
index 40bb511..a98d3c1 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -211,18 +211,16 @@ EXPORT_SYMBOL_GPL(torture_onoff_cleanup);
/*
* Print online/offline testing statistics.
*/
-char *torture_onoff_stats(char *page)
+void torture_onoff_stats(void)
{
#ifdef CONFIG_HOTPLUG_CPU
- 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);
+ pr_cont("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);
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
- return page;
}
EXPORT_SYMBOL_GPL(torture_onoff_stats);
--
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