3 files changed, 299 insertions, 0 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 944239296f13..dde1d46f77e5 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -284,6 +284,17 @@ config KMEMTRACE
 
           If unsure, say N.
 
+config WORKQUEUE_TRACER
+        bool "Trace workqueues"
+        select TRACING
+        help
+          The workqueue tracer provides some statistical informations
+          about each cpu workqueue thread such as the number of the
+          works inserted and executed since their creation. It can help
+          to evaluate the amount of work each of them have to perform.
+          For example it can help a developer to decide whether he should
+          choose a per cpu workqueue instead of a singlethreaded one.
+
 
 config DYNAMIC_FTRACE
         bool "enable/disable ftrace tracepoints dynamically"
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index 05c9182061de..f76d48f3527d 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -36,5 +36,6 @@ obj-$(CONFIG_TRACE_BRANCH_PROFILING) += trace_branch.o
 obj-$(CONFIG_HW_BRANCH_TRACER) += trace_hw_branches.o
 obj-$(CONFIG_POWER_TRACER) += trace_power.o
 obj-$(CONFIG_KMEMTRACE) += kmemtrace.o
+obj-$(CONFIG_WORKQUEUE_TRACER) += trace_workqueue.o
 
 libftrace-y := ftrace.o
diff --git a/kernel/trace/trace_workqueue.c b/kernel/trace/trace_workqueue.c
new file mode 100644
index 000000000000..f8118d39ca9b
--- /dev/null
+++ b/kernel/trace/trace_workqueue.c
@@ -0,0 +1,287 @@
+/*
+ * Workqueue statistical tracer.
+ *
+ * Copyright (C) 2008 Frederic Weisbecker <fweisbec@gmail.com>
+ *
+ */
+
+
+#include <trace/workqueue.h>
+#include <linux/list.h>
+#include "trace_stat.h"
+#include "trace.h"
+
+
+/* A cpu workqueue thread */
+struct cpu_workqueue_stats {
+        struct list_head            list;
+/* Useful to know if we print the cpu headers */
+        bool                        first_entry;
+        int                         cpu;
+        pid_t                       pid;
+/* Can be inserted from interrupt or user context, need to be atomic */
+        atomic_t                    inserted;
+/*
+ *  Don't need to be atomic, works are serialized in a single workqueue thread
+ *  on a single CPU.
+ */
+        unsigned int                executed;
+};
+
+/* List of workqueue threads on one cpu */
+struct workqueue_global_stats {
+        struct list_head        list;
+        spinlock_t              lock;
+};
+
+/* Don't need a global lock because allocated before the workqueues, and
+ * never freed.
+ */
+static struct workqueue_global_stats *all_workqueue_stat;
+
+/* Insertion of a work */
+static void
+probe_workqueue_insertion(struct task_struct *wq_thread,
+                          struct work_struct *work)
+{
+        int cpu = cpumask_first(&wq_thread->cpus_allowed);
+        struct cpu_workqueue_stats *node, *next;
+        unsigned long flags;
+
+        spin_lock_irqsave(&all_workqueue_stat[cpu].lock, flags);
+        list_for_each_entry_safe(node, next, &all_workqueue_stat[cpu].list,
+                                                        list) {
+                if (node->pid == wq_thread->pid) {
+                        atomic_inc(&node->inserted);
+                        goto found;
+                }
+        }
+        pr_debug("trace_workqueue: entry not found\n");
+found:
+        spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
+}
+
+/* Execution of a work */
+static void
+probe_workqueue_execution(struct task_struct *wq_thread,
+                          struct work_struct *work)
+{
+        int cpu = cpumask_first(&wq_thread->cpus_allowed);
+        struct cpu_workqueue_stats *node, *next;
+        unsigned long flags;
+
+        spin_lock_irqsave(&all_workqueue_stat[cpu].lock, flags);
+        list_for_each_entry_safe(node, next, &all_workqueue_stat[cpu].list,
+                                                        list) {
+                if (node->pid == wq_thread->pid) {
+                        node->executed++;
+                        goto found;
+                }
+        }
+        pr_debug("trace_workqueue: entry not found\n");
+found:
+        spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
+}
+
+/* Creation of a cpu workqueue thread */
+static void probe_workqueue_creation(struct task_struct *wq_thread, int cpu)
+{
+        struct cpu_workqueue_stats *cws;
+        unsigned long flags;
+
+        WARN_ON(cpu < 0 || cpu >= num_possible_cpus());
+
+        /* Workqueues are sometimes created in atomic context */
+        cws = kzalloc(sizeof(struct cpu_workqueue_stats), GFP_ATOMIC);
+        if (!cws) {
+                pr_warning("trace_workqueue: not enough memory\n");
+                return;
+        }
+        tracing_record_cmdline(wq_thread);
+
+        INIT_LIST_HEAD(&cws->list);
+        cws->cpu = cpu;
+
+        cws->pid = wq_thread->pid;
+
+        spin_lock_irqsave(&all_workqueue_stat[cpu].lock, flags);
+        if (list_empty(&all_workqueue_stat[cpu].list))
+                cws->first_entry = true;
+        list_add_tail(&cws->list, &all_workqueue_stat[cpu].list);
+        spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
+}
+
+/* Destruction of a cpu workqueue thread */
+static void probe_workqueue_destruction(struct task_struct *wq_thread)
+{
+        /* Workqueue only execute on one cpu */
+        int cpu = cpumask_first(&wq_thread->cpus_allowed);
+        struct cpu_workqueue_stats *node, *next;
+        unsigned long flags;
+
+        spin_lock_irqsave(&all_workqueue_stat[cpu].lock, flags);
+        list_for_each_entry_safe(node, next, &all_workqueue_stat[cpu].list,
+                                                        list) {
+                if (node->pid == wq_thread->pid) {
+                        list_del(&node->list);
+                        kfree(node);
+                        goto found;
+                }
+        }
+
+        pr_debug("trace_workqueue: don't find workqueue to destroy\n");
+found:
+        spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
+
+}
+
+static struct cpu_workqueue_stats *workqueue_stat_start_cpu(int cpu)
+{
+        unsigned long flags;
+        struct cpu_workqueue_stats *ret = NULL;
+
+
+        spin_lock_irqsave(&all_workqueue_stat[cpu].lock, flags);
+
+        if (!list_empty(&all_workqueue_stat[cpu].list))
+                ret = list_entry(all_workqueue_stat[cpu].list.next,
+                                 struct cpu_workqueue_stats, list);
+
+        spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
+
+        return ret;
+}
+
+static void *workqueue_stat_start(void)
+{
+        int cpu;
+        void *ret = NULL;
+
+        for_each_possible_cpu(cpu) {
+                ret = workqueue_stat_start_cpu(cpu);
+                if (ret)
+                        return ret;
+        }
+        return NULL;
+}
+
+static void *workqueue_stat_next(void *prev, int idx)
+{
+        struct cpu_workqueue_stats *prev_cws = prev;
+        int cpu = prev_cws->cpu;
+        unsigned long flags;
+        void *ret = NULL;
+
+        spin_lock_irqsave(&all_workqueue_stat[cpu].lock, flags);
+        if (list_is_last(&prev_cws->list, &all_workqueue_stat[cpu].list)) {
+                spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
+                for (++cpu ; cpu < num_possible_cpus(); cpu++) {
+                        ret = workqueue_stat_start_cpu(cpu);
+                        if (ret)
+                                return ret;
+                }
+                return NULL;
+        }
+        spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
+
+        return list_entry(prev_cws->list.next, struct cpu_workqueue_stats,
+                          list);
+}
+
+static int workqueue_stat_show(struct seq_file *s, void *p)
+{
+        struct cpu_workqueue_stats *cws = p;
+        unsigned long flags;
+        int cpu = cws->cpu;
+
+        seq_printf(s, "%3d %6d     %6u       %s\n", cws->cpu,
+                   atomic_read(&cws->inserted),
+                   cws->executed,
+                   trace_find_cmdline(cws->pid));
+
+        spin_lock_irqsave(&all_workqueue_stat[cpu].lock, flags);
+        if (&cws->list == all_workqueue_stat[cpu].list.next)
+                seq_printf(s, "\n");
+        spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
+
+        return 0;
+}
+
+static int workqueue_stat_headers(struct seq_file *s)
+{
+        seq_printf(s, "# CPU  INSERTED  EXECUTED   NAME\n");
+        seq_printf(s, "# |      |         |          |\n\n");
+        return 0;
+}
+
+struct tracer_stat workqueue_stats __read_mostly = {
+        .name = "workqueues",
+        .stat_start = workqueue_stat_start,
+        .stat_next = workqueue_stat_next,
+        .stat_show = workqueue_stat_show,
+        .stat_headers = workqueue_stat_headers
+};
+
+
+int __init stat_workqueue_init(void)
+{
+        if (register_stat_tracer(&workqueue_stats)) {
+                pr_warning("Unable to register workqueue stat tracer\n");
+                return 1;
+        }
+
+        return 0;
+}
+fs_initcall(stat_workqueue_init);
+
+/*
+ * Workqueues are created very early, just after pre-smp initcalls.
+ * So we must register our tracepoints at this stage.
+ */
+int __init trace_workqueue_early_init(void)
+{
+        int ret, cpu;
+
+        ret = register_trace_workqueue_insertion(probe_workqueue_insertion);
+        if (ret)
+                goto out;
+
+        ret = register_trace_workqueue_execution(probe_workqueue_execution);
+        if (ret)
+                goto no_insertion;
+
+        ret = register_trace_workqueue_creation(probe_workqueue_creation);
+        if (ret)
+                goto no_execution;
+
+        ret = register_trace_workqueue_destruction(probe_workqueue_destruction);
+        if (ret)
+                goto no_creation;
+
+        all_workqueue_stat = kmalloc(sizeof(struct workqueue_global_stats)
+                                     * num_possible_cpus(), GFP_KERNEL);
+
+        if (!all_workqueue_stat) {
+                pr_warning("trace_workqueue: not enough memory\n");
+                goto no_creation;
+        }
+
+        for_each_possible_cpu(cpu) {
+                spin_lock_init(&all_workqueue_stat[cpu].lock);
+                INIT_LIST_HEAD(&all_workqueue_stat[cpu].list);
+        }
+
+        return 0;
+
+no_creation:
+        unregister_trace_workqueue_creation(probe_workqueue_creation);
+no_execution:
+        unregister_trace_workqueue_execution(probe_workqueue_execution);
+no_insertion:
+        unregister_trace_workqueue_insertion(probe_workqueue_insertion);
+out:
+        pr_warning("trace_workqueue: unable to trace workqueues\n");
+
+        return 1;
+}
+early_initcall(trace_workqueue_early_init);