From: George Beshers <gbeshers@redhat.com>
Date: Fri, 4 Jan 2008 15:31:18 -0500
Subject: [misc] increase softlockup timeout maximum
Message-id: 477E9796.3010505@redhat.com
O-Subject: Re: [RHEL5.2 PATCH] increase softlockup timeout maximum
Bugzilla: 253124

This is BZ#253124

Most of the need for this was obviated by Prarit's patch to allow the
softlockup threshold to be adjusted via /proc/sys/kernel/softlockup_thresh
which was backported from upstream.

This patch increases just the maximum threshold that can be
set and is only necessary for systems >128p and 512Gb --- and
then only if the systems are severely stressed.

NOTE: if the hwcert team decides to reduce the amount of
 swapping needed to certify large systems this probably won't
 be needed.

NOTE: I am working on a patch to reduce the lock contention
 with swapping but it isn't ready for prime time yet.

Please comment or ACK.

Acked-by: Prarit Bhargava <prarit@redhat.com>

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 5d06c4b..d248271 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -83,6 +83,12 @@ extern int proc_unknown_nmi_panic(ctl_table *, int, struct file *,
 				  void __user *, size_t *, loff_t *);
 #endif
 
+#ifdef CONFIG_DETECT_SOFTLOCKUP
+int proc_dointvec_minmax_softlockup(
+                  ctl_table *table, int write, struct file *filp,
+		  void __user *buffer, size_t *lenp, loff_t *ppos);
+#endif
+
 extern unsigned int vdso_enabled, vdso_populate;
 
 int exec_shield = (1<<0);
@@ -109,6 +115,7 @@ __setup("exec-shield=", setup_exec_shield);
 #ifdef CONFIG_DETECT_SOFTLOCKUP
 static int one = 1;
 static int sixty = 60;
+static int threehundred = 300;
 #endif
 
 static int zero;
@@ -794,7 +801,7 @@ static ctl_table kern_table[] = {
 		.data		= &softlockup_thresh,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= &proc_dointvec_minmax,
+		.proc_handler	= &proc_dointvec_minmax_softlockup,
 		.strategy	= &sysctl_intvec,
 		.extra1		= &one,
 		.extra2		= &sixty,
@@ -2064,6 +2071,26 @@ int proc_dointvec_minmax(ctl_table *table, int write, struct file *filp,
 				do_proc_dointvec_minmax_conv, &param);
 }
 
+#ifdef CONFIG_DETECT_SOFTLOCKUP
+/*
+ * proc_dointvec_minmax_softlockup -- add conditional to handle
+ * large systems.
+ */
+int proc_dointvec_minmax_softlockup(
+                  ctl_table *table, int write, struct file *filp,
+		  void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct do_proc_dointvec_minmax_conv_param param = {
+		.min = (int *) table->extra1,
+		.max = (int *) table->extra2,
+	};
+	if (num_online_cpus() > 128)
+		param.max = &threehundred;
+	return do_proc_dointvec(table, write, filp, buffer, lenp, ppos,
+				do_proc_dointvec_minmax_conv, &param);
+}
+#endif
+
 static int do_proc_doulongvec_minmax(ctl_table *table, int write,
 				     struct file *filp,
 				     void __user *buffer,