From ca5a3f13bf247561e64ef2323b3dd28a2c3b880d Mon Sep 17 00:00:00 2001
From: Rik van Riel <riel@redhat.com>
Date: Thu, 12 Mar 2015 17:47:00 -0400
Subject: [PATCH 3/3] parse isolcpus= from /proc/cmdline to set up banned_cpus

When the user specifies a range of CPUs to be isolated from system
tasks with isolcpus= on the kernel command line, it would be nice
if those CPUs could automatically be excluded from getting interrupts
routed to them, as well.

This patch does that, by looking at /proc/cmdline

The environment variable IRQBALANCE_BANNED_CPUS will override the
automatically detectable banned_cpus.

Signed-off-by: Rik van Riel <riel@redhat.com>
---
 cputree.c    | 44 ++++++++++++++++++++++++++++++++++++++++++++
 irqbalance.c |  4 ----
 2 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/cputree.c b/cputree.c
index 8b8cf5e..cfa70b6 100644
--- a/cputree.c
+++ b/cputree.c
@@ -58,6 +58,48 @@ cpumask_t cpu_possible_map;
 */
 cpumask_t unbanned_cpus;
 
+/*
+ * By default do not place IRQs on CPUs the kernel keeps isolated,
+ * as specified through the isolcpus= boot commandline. Users can
+ * override this with the IRQBALANCE_BANNED_CPUS environment variable.
+ */
+static void setup_banned_cpus(void)
+{
+	FILE *file;
+	char *c, *line = NULL;
+	size_t size = 0;
+	const char *isolcpus = "isolcpus=";
+	char buffer[4096];
+
+	/* A manually specified cpumask overrides auto-detection. */
+	if (getenv("IRQBALANCE_BANNED_CPUS"))  {
+		cpumask_parse_user(getenv("IRQBALANCE_BANNED_CPUS"), strlen(getenv("IRQBALANCE_BANNED_CPUS")), banned_cpus);
+		goto out;
+	}
+
+	file = fopen("/proc/cmdline", "r");
+	if (!file)
+		goto out;
+
+	if (getline(&line, &size, file) <= 0)
+		goto out;
+
+	if ((c = strstr(line, isolcpus))) {
+		char *end;
+		int len;
+
+		c += strlen(isolcpus);
+		for (end = c; *end != ' ' && *end != '\0' && *end != '\n'; end++);
+		len = end - c;
+
+		cpulist_parse(c, len, banned_cpus);
+	}
+
+ out:
+	cpumask_scnprintf(buffer, 4096, banned_cpus);
+	log(TO_CONSOLE, LOG_INFO, "Isolated CPUs: %s\n", buffer);
+}
+
 static struct topo_obj* add_cache_domain_to_package(struct topo_obj *cache, 
 						    int packageid, cpumask_t package_mask)
 {
@@ -372,6 +414,8 @@ void parse_cpu_tree(void)
 	DIR *dir;
 	struct dirent *entry;
 
+	setup_banned_cpus();
+
 	cpus_complement(unbanned_cpus, banned_cpus);
 
 	dir = opendir("/sys/devices/system/cpu");
diff --git a/irqbalance.c b/irqbalance.c
index a5079b9..e4f3b93 100644
--- a/irqbalance.c
+++ b/irqbalance.c
@@ -276,10 +276,6 @@ int main(int argc, char** argv)
  	 */
 	openlog(argv[0], 0, LOG_DAEMON);
 
-	if (getenv("IRQBALANCE_BANNED_CPUS"))  {
-		cpumask_parse_user(getenv("IRQBALANCE_BANNED_CPUS"), strlen(getenv("IRQBALANCE_BANNED_CPUS")), banned_cpus);
-	}
-
 	if (getenv("IRQBALANCE_ONESHOT")) 
 		one_shot_mode=1;
 
-- 
2.1.0