3 files changed, 130 insertions, 2 deletions

diff --git a/include/linux/slow-work.h b/include/linux/slow-work.h
index 4dd754af393e..8262809dfa8b 100644
--- a/include/linux/slow-work.h
+++ b/include/linux/slow-work.h
@@ -14,6 +14,8 @@
 
 #ifdef CONFIG_SLOW_WORK
 
+#include <linux/sysctl.h>
+
 struct slow_work;
 
 /*
@@ -83,6 +85,9 @@ extern int slow_work_enqueue(struct slow_work *work);
 extern int slow_work_register_user(void);
 extern void slow_work_unregister_user(void);
 
+#ifdef CONFIG_SYSCTL
+extern ctl_table slow_work_sysctls[];
+#endif
 
 #endif /* CONFIG_SLOW_WORK */
 #endif /* _LINUX_SLOW_WORK_H */
diff --git a/kernel/slow-work.c b/kernel/slow-work.c
index 454abb21c8bd..3f65900aa3cb 100644
--- a/kernel/slow-work.c
+++ b/kernel/slow-work.c
@@ -14,7 +14,6 @@
 #include <linux/kthread.h>
 #include <linux/freezer.h>
 #include <linux/wait.h>
-#include <asm/system.h>
 
 #define SLOW_WORK_CULL_TIMEOUT (5 * HZ) /* cull threads 5s after running out of
                                          * things to do */
@@ -24,6 +23,14 @@
 static void slow_work_cull_timeout(unsigned long);
 static void slow_work_oom_timeout(unsigned long);
 
+#ifdef CONFIG_SYSCTL
+static int slow_work_min_threads_sysctl(struct ctl_table *, int, struct file *,
+                                        void __user *, size_t *, loff_t *);
+
+static int slow_work_max_threads_sysctl(struct ctl_table *, int , struct file *,
+                                        void __user *, size_t *, loff_t *);
+#endif
+
 /*
  * The pool of threads has at least min threads in it as long as someone is
  * using the facility, and may have as many as max.
@@ -34,6 +41,51 @@ static unsigned slow_work_min_threads = 2;
 static unsigned slow_work_max_threads = 4;
 static unsigned vslow_work_proportion = 50; /* % of threads that may process
                                              * very slow work */
+
+#ifdef CONFIG_SYSCTL
+static const int slow_work_min_min_threads = 2;
+static int slow_work_max_max_threads = 255;
+static const int slow_work_min_vslow = 1;
+static const int slow_work_max_vslow = 99;
+
+ctl_table slow_work_sysctls[] = {
+        {
+                .ctl_name       = CTL_UNNUMBERED,
+                .procname       = "min-threads",
+                .data           = &slow_work_min_threads,
+                .maxlen         = sizeof(unsigned),
+                .mode           = 0644,
+                .proc_handler   = slow_work_min_threads_sysctl,
+                .extra1         = (void *) &slow_work_min_min_threads,
+                .extra2         = &slow_work_max_threads,
+        },
+        {
+                .ctl_name       = CTL_UNNUMBERED,
+                .procname       = "max-threads",
+                .data           = &slow_work_max_threads,
+                .maxlen         = sizeof(unsigned),
+                .mode           = 0644,
+                .proc_handler   = slow_work_max_threads_sysctl,
+                .extra1         = &slow_work_min_threads,
+                .extra2         = (void *) &slow_work_max_max_threads,
+        },
+        {
+                .ctl_name       = CTL_UNNUMBERED,
+                .procname       = "vslow-percentage",
+                .data           = &vslow_work_proportion,
+                .maxlen         = sizeof(unsigned),
+                .mode           = 0644,
+                .proc_handler   = &proc_dointvec_minmax,
+                .extra1         = (void *) &slow_work_min_vslow,
+                .extra2         = (void *) &slow_work_max_vslow,
+        },
+        { .ctl_name = 0 }
+};
+#endif
+
+/*
+ * The active state of the thread pool
+ */
 static atomic_t slow_work_thread_count;
 static atomic_t vslow_work_executing_count;
 
@@ -427,6 +479,64 @@ static void slow_work_oom_timeout(unsigned long data)
         slow_work_may_not_start_new_thread = false;
 }
 
+#ifdef CONFIG_SYSCTL
+/*
+ * Handle adjustment of the minimum number of threads
+ */
+static int slow_work_min_threads_sysctl(struct ctl_table *table, int write,
+                                        struct file *filp, void __user *buffer,
+                                        size_t *lenp, loff_t *ppos)
+{
+        int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
+        int n;
+
+        if (ret == 0) {
+                mutex_lock(&slow_work_user_lock);
+                if (slow_work_user_count > 0) {
+                        /* see if we need to start or stop threads */
+                        n = atomic_read(&slow_work_thread_count) -
+                                slow_work_min_threads;
+
+                        if (n < 0 && !slow_work_may_not_start_new_thread)
+                                slow_work_enqueue(&slow_work_new_thread);
+                        else if (n > 0)
+                                mod_timer(&slow_work_cull_timer,
+                                          jiffies + SLOW_WORK_CULL_TIMEOUT);
+                }
+                mutex_unlock(&slow_work_user_lock);
+        }
+
+        return ret;
+}
+
+/*
+ * Handle adjustment of the maximum number of threads
+ */
+static int slow_work_max_threads_sysctl(struct ctl_table *table, int write,
+                                        struct file *filp, void __user *buffer,
+                                        size_t *lenp, loff_t *ppos)
+{
+        int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
+        int n;
+
+        if (ret == 0) {
+                mutex_lock(&slow_work_user_lock);
+                if (slow_work_user_count > 0) {
+                        /* see if we need to stop threads */
+                        n = slow_work_max_threads -
+                                atomic_read(&slow_work_thread_count);
+
+                        if (n < 0)
+                                mod_timer(&slow_work_cull_timer,
+                                          jiffies + SLOW_WORK_CULL_TIMEOUT);
+                }
+                mutex_unlock(&slow_work_user_lock);
+        }
+
+        return ret;
+}
+#endif /* CONFIG_SYSCTL */
+
 /**
  * slow_work_register_user - Register a user of the facility
  *
@@ -516,8 +626,12 @@ static int __init init_slow_work(void)
 {
         unsigned nr_cpus = num_possible_cpus();
 
-        if (nr_cpus > slow_work_max_threads)
+        if (slow_work_max_threads < nr_cpus)
                 slow_work_max_threads = nr_cpus;
+#ifdef CONFIG_SYSCTL
+        if (slow_work_max_max_threads < nr_cpus * 2)
+                slow_work_max_max_threads = nr_cpus * 2;
+#endif
         return 0;
 }
 
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 5ec4543dfc06..82350f8f04f6 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -48,6 +48,7 @@
 #include <linux/acpi.h>
 #include <linux/reboot.h>
 #include <linux/ftrace.h>
+#include <linux/slow-work.h>
 
 #include <asm/uaccess.h>
 #include <asm/processor.h>
@@ -897,6 +898,14 @@ static struct ctl_table kern_table[] = {
                 .proc_handler   = &scan_unevictable_handler,
         },
 #endif
+#ifdef CONFIG_SLOW_WORK
+        {
+                .ctl_name       = CTL_UNNUMBERED,
+                .procname       = "slow-work",
+                .mode           = 0555,
+                .child          = slow_work_sysctls,
+        },
+#endif
 /*
  * NOTE: do not add new entries to this table unless you have read
  * Documentation/sysctl/ctl_unnumbered.txt