Re: [PATCH 1/1] rcutorture: fixes for printing message buffer

From: Paul E. McKenney
Date: Wed Aug 13 2014 - 17:17:34 EST

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On Mon, Jul 14, 2014 at 09:26:32AM -0400, Pranith Kumar wrote:
> On 07/11/2014 04:37 PM, Joe Perches wrote:
> > On Fri, 2014-07-11 at 16:30 -0400, Pranith Kumar wrote:
> >> Use snprintf() instead of sprintf() for writing to the message buffer.
> >> Also use vmalloc() for the allocation of the message buffer. Since pr_alert() is
> >> limited to print LOG_LINE_MAX characters at a time, we print the buffer in a
> >> loop one line at a time.
> >>
> >> I tested this using the parse-torture.sh script as follows:
> >
> > Did you see the patch I sent you?
> > https://lkml.org/lkml/2014/6/20/604
> >
> > It doesn't need a vmalloc.
> > What is wrong with that approach?
> >
> >
>
> Hi Paul,
>
> Please find an alternative patch as suggested by Joe.

Queued for 3.18, thank you both!

Thanx, Paul

> >From 0a3050d5ac910cb5f488e0a0dfe44cde06af1259 Mon Sep 17 00:00:00 2001
> From: Pranith Kumar <bobby.prani@xxxxxxxxx>
> Date: Mon, 14 Jul 2014 09:16:15 -0400
> Subject: [PATCH 1/1] rcu: Use pr_alert/pr_cont for printing logs
>
> User pr_alert/pr_cont for printing the logs from rcutorture module directly
> instead of writing it to a buffer and then printing it. This allows us from not
> having to allocate such buffers. Also remove a resulting empty function.
>
> I tested this using the parse-torture.sh script as follows:
>
> $ dmesg | grep torture > log.txt
> $ bash parse-torture.sh log.txt test
> $
>
> There were no warnings which means that parsing went fine.
>
> Signed-off-by: Joe Percesh <joe@xxxxxxxxxxx>
> Signed-off-by: Pranith Kumar <bobby.prani@xxxxxxxxx>
> ---
> include/linux/torture.h | 2 +-
> kernel/rcu/rcutorture.c | 127 +++++++++++++++++++++---------------------------
> kernel/torture.c | 16 +++---
> 3 files changed, 64 insertions(+), 81 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 5ec0452..3e35f1b 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 +1031,15 @@ rcu_torture_reader(void *arg)
> }
>
> /*
> - * Create an RCU-torture statistics message in the specified buffer.
> + * Print torture statistics. Caller must ensure that there is only
> + * one call to this function at a given time!!! This is normally
> + * accomplished by relying on the module system to only have one copy
> + * of the module loaded, and then by giving the rcu_torture_stats
> + * kthread full control (or the init/cleanup functions when rcu_torture_stats
> + * thread is not running).
> */
> static void
> -rcu_torture_printk(char *page)
> +rcu_torture_stats_print(void)
> {
> int cpu;
> int i;
> @@ -1052,55 +1057,60 @@ 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 +1119,9 @@ 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();
> }
> @@ -1120,30 +1129,6 @@ rcu_torture_printk(char *page)
> }
>
> /*
> - * Print torture statistics. Caller must ensure that there is only
> - * one call to this function at a given time!!! This is normally
> - * accomplished by relying on the module system to only have one copy
> - * of the module loaded, and then by giving the rcu_torture_stats
> - * kthread full control (or the init/cleanup functions when rcu_torture_stats
> - * thread is not running).
> - */
> -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);
> -}
> -
> -/*
> * Periodically prints torture statistics, if periodic statistics printing
> * was specified via the stat_interval module parameter.
> */
> diff --git a/kernel/torture.c b/kernel/torture.c
> index d600af2..ede8b25 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);
>
> --
> 2.0.1
>

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