[PATCH tip/core/rcu 12/17] torture: Throttle VERBOSE_TOROUT_*() output

[paulmck]

From: "Paul E. McKenney" <paulmck@xxxxxxxxxx>

This commit adds kernel boot parameters torture.verbose_sleep_frequency
and torture.verbose_sleep_duration, which allow VERBOSE_TOROUT_*() output
to be throttled with periodic sleeps on large systems.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
 Documentation/admin-guide/kernel-parameters.txt |  8 ++++++++
 include/linux/torture.h                         | 15 +++++++++++++--
 kernel/torture.c                                | 20 ++++++++++++++++++++
 3 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 29ea816..5ce95dd 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5337,6 +5337,14 @@
 			are running concurrently, especially on systems
 			with rotating-rust storage.
 
+	torture.verbose_sleep_frequency= [KNL]
+			Specifies how many verbose printk()s should be
+			emitted between each sleep.  The default of zero
+			disables verbose-printk() sleeping.
+
+	torture.verbose_sleep_duration= [KNL]
+			Duration of each verbose-printk() sleep in jiffies.
+
 	tp720=		[HW,PS2]
 
 	tpm_suspend_pcr=[HW,TPM]
diff --git a/include/linux/torture.h b/include/linux/torture.h
index 32941f8..d62d13c 100644
--- a/include/linux/torture.h
+++ b/include/linux/torture.h
@@ -32,9 +32,20 @@
 #define TOROUT_STRING(s) \
 	pr_alert("%s" TORTURE_FLAG " %s\n", torture_type, s)
 #define VERBOSE_TOROUT_STRING(s) \
-	do { if (verbose) pr_alert("%s" TORTURE_FLAG " %s\n", torture_type, s); } while (0)
+do {										\
+	if (verbose) {								\
+		verbose_torout_sleep();						\
+		pr_alert("%s" TORTURE_FLAG " %s\n", torture_type, s);		\
+	}									\
+} while (0)
 #define VERBOSE_TOROUT_ERRSTRING(s) \
-	do { if (verbose) pr_alert("%s" TORTURE_FLAG "!!! %s\n", torture_type, s); } while (0)
+do {										\
+	if (verbose) {								\
+		verbose_torout_sleep();						\
+		pr_alert("%s" TORTURE_FLAG "!!! %s\n", torture_type, s);	\
+	}									\
+} while (0)
+void verbose_torout_sleep(void);
 
 /* Definitions for online/offline exerciser. */
 typedef void torture_ofl_func(void);
diff --git a/kernel/torture.c b/kernel/torture.c
index 7ad5c96..93eeeb2 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -48,6 +48,12 @@ module_param(disable_onoff_at_boot, bool, 0444);
 static bool ftrace_dump_at_shutdown;
 module_param(ftrace_dump_at_shutdown, bool, 0444);
 
+static int verbose_sleep_frequency;
+module_param(verbose_sleep_frequency, int, 0444);
+
+static int verbose_sleep_duration = 1;
+module_param(verbose_sleep_duration, int, 0444);
+
 static char *torture_type;
 static int verbose;
 
@@ -58,6 +64,20 @@ static int verbose;
 static int fullstop = FULLSTOP_RMMOD;
 static DEFINE_MUTEX(fullstop_mutex);
 
+static atomic_t verbose_sleep_counter;
+
+/*
+ * Sleep if needed from VERBOSE_TOROUT*().
+ */
+void verbose_torout_sleep(void)
+{
+	if (verbose_sleep_frequency > 0 &&
+	    verbose_sleep_duration > 0 &&
+	    !(atomic_inc_return(&verbose_sleep_counter) % verbose_sleep_frequency))
+		schedule_timeout_uninterruptible(verbose_sleep_duration);
+}
+EXPORT_SYMBOL_GPL(verbose_torout_sleep);
+
 /*
  * Schedule a high-resolution-timer sleep in nanoseconds, with a 32-bit
  * nanosecond random fuzz.  This function and its friends desynchronize
-- 
2.9.5