[RFC/PATCH] trace: Remove unused workqueue tracer

Stephen Boyd
2012-04-09T18:00:33Z

This tracer was temporarily removed in 6416669 (workqueue:
temporarily remove workqueue tracing, 2010-06-29) but never
reinstated after concurrency managed workqueues were completed.
For almost two years it hasn't been compilable so it seems nobody
is using it. Delete it.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
---

I noticed this while poking through the tracer code. This patch
is meant to incite discussion.

Can this tracer be salvaged? In it's simplest form I suppose we can
trace the number of queued, active, running, and completed work items.

kernel/trace/Makefile | 1 -
kernel/trace/trace_workqueue.c | 300 ----------------------------------------
2 files changed, 301 deletions(-)
delete mode 100644 kernel/trace/trace_workqueue.c

diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index 5f39a07..b3afe0e 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -41,7 +41,6 @@ obj-$(CONFIG_STACK_TRACER) += trace_stack.o
obj-$(CONFIG_MMIOTRACE) += trace_mmiotrace.o
obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += trace_functions_graph.o
obj-$(CONFIG_TRACE_BRANCH_PROFILING) += trace_branch.o
-obj-$(CONFIG_WORKQUEUE_TRACER) += trace_workqueue.o
obj-$(CONFIG_BLK_DEV_IO_TRACE) += blktrace.o
ifeq ($(CONFIG_BLOCK),y)
obj-$(CONFIG_EVENT_TRACING) += blktrace.o
diff --git a/kernel/trace/trace_workqueue.c b/kernel/trace/trace_workqueue.c
deleted file mode 100644
index 209b379..0000000
--- a/kernel/trace/trace_workqueue.c
+++ /dev/null
@@ -1,300 +0,0 @@
-/*
- * Workqueue statistical tracer.
- *
- * Copyright (C) 2008 Frederic Weisbecker <fweisbec@gmail.com>
- *
- */
-
-
-#include <trace/events/workqueue.h>
-#include <linux/list.h>
-#include <linux/percpu.h>
-#include <linux/slab.h>
-#include <linux/kref.h>
-#include "trace_stat.h"
-#include "trace.h"
-
-
-/* A cpu workqueue thread */
-struct cpu_workqueue_stats {
- struct list_head list;
- struct kref kref;
- 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 DEFINE_PER_CPU(struct workqueue_global_stats, all_workqueue_stat);
-#define workqueue_cpu_stat(cpu) (&per_cpu(all_workqueue_stat, cpu))
-
-static void cpu_workqueue_stat_free(struct kref *kref)
-{
- kfree(container_of(kref, struct cpu_workqueue_stats, kref));
-}
-
-/* Insertion of a work */
-static void
-probe_workqueue_insertion(void *ignore,
- struct task_struct *wq_thread,
- struct work_struct *work)
-{
- int cpu = cpumask_first(&wq_thread->cpus_allowed);
- struct cpu_workqueue_stats *node;
- unsigned long flags;
-
- spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
- list_for_each_entry(node, &workqueue_cpu_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(&workqueue_cpu_stat(cpu)->lock, flags);
-}
-
-/* Execution of a work */
-static void
-probe_workqueue_execution(void *ignore,
- struct task_struct *wq_thread,
- struct work_struct *work)
-{
- int cpu = cpumask_first(&wq_thread->cpus_allowed);
- struct cpu_workqueue_stats *node;
- unsigned long flags;
-
- spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
- list_for_each_entry(node, &workqueue_cpu_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(&workqueue_cpu_stat(cpu)->lock, flags);
-}
-
-/* Creation of a cpu workqueue thread */
-static void probe_workqueue_creation(void *ignore,
- struct task_struct *wq_thread, int cpu)
-{
- struct cpu_workqueue_stats *cws;
- unsigned long flags;
-
- WARN_ON(cpu < 0);
-
- /* 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;
- }
- INIT_LIST_HEAD(&cws->list);
- kref_init(&cws->kref);
- cws->cpu = cpu;
- cws->pid = wq_thread->pid;
-
- spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
- list_add_tail(&cws->list, &workqueue_cpu_stat(cpu)->list);
- spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
-}
-
-/* Destruction of a cpu workqueue thread */
-static void
-probe_workqueue_destruction(void *ignore, 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(&workqueue_cpu_stat(cpu)->lock, flags);
- list_for_each_entry_safe(node, next, &workqueue_cpu_stat(cpu)->list,
- list) {
- if (node->pid == wq_thread->pid) {
- list_del(&node->list);
- kref_put(&node->kref, cpu_workqueue_stat_free);
- goto found;
- }
- }
-
- pr_debug("trace_workqueue: don't find workqueue to destroy\n");
-found:
- spin_unlock_irqrestore(&workqueue_cpu_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(&workqueue_cpu_stat(cpu)->lock, flags);
-
- if (!list_empty(&workqueue_cpu_stat(cpu)->list)) {
- ret = list_entry(workqueue_cpu_stat(cpu)->list.next,
- struct cpu_workqueue_stats, list);
- kref_get(&ret->kref);
- }
-
- spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
-
- return ret;
-}
-
-static void *workqueue_stat_start(struct tracer_stat *trace)
-{
- 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;
- struct cpu_workqueue_stats *ret;
- int cpu = prev_cws->cpu;
- unsigned long flags;
-
- spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
- if (list_is_last(&prev_cws->list, &workqueue_cpu_stat(cpu)->list)) {
- spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
- do {
- cpu = cpumask_next(cpu, cpu_possible_mask);
- if (cpu >= nr_cpu_ids)
- return NULL;
- } while (!(ret = workqueue_stat_start_cpu(cpu)));
- return ret;
- } else {
- ret = list_entry(prev_cws->list.next,
- struct cpu_workqueue_stats, list);
- kref_get(&ret->kref);
- }
- spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
-
- return ret;
-}
-
-static int workqueue_stat_show(struct seq_file *s, void *p)
-{
- struct cpu_workqueue_stats *cws = p;
- struct pid *pid;
- struct task_struct *tsk;
-
- pid = find_get_pid(cws->pid);
- if (pid) {
- tsk = get_pid_task(pid, PIDTYPE_PID);
- if (tsk) {
- seq_printf(s, "%3d %6d %6u %s\n", cws->cpu,
- atomic_read(&cws->inserted), cws->executed,
- tsk->comm);
- put_task_struct(tsk);
- }
- put_pid(pid);
- }
-
- return 0;
-}
-
-static void workqueue_stat_release(void *stat)
-{
- struct cpu_workqueue_stats *node = stat;
-
- kref_put(&node->kref, cpu_workqueue_stat_free);
-}
-
-static int workqueue_stat_headers(struct seq_file *s)
-{
- seq_printf(s, "# CPU INSERTED EXECUTED NAME\n");
- seq_printf(s, "# | | | |\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_release = workqueue_stat_release,
- .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;
-
- for_each_possible_cpu(cpu) {
- spin_lock_init(&workqueue_cpu_stat(cpu)->lock);
- INIT_LIST_HEAD(&workqueue_cpu_stat(cpu)->list);
- }
-
- ret = register_trace_workqueue_insertion(probe_workqueue_insertion, NULL);
- if (ret)
- goto out;
-
- ret = register_trace_workqueue_execution(probe_workqueue_execution, NULL);
- if (ret)
- goto no_insertion;
-
- ret = register_trace_workqueue_creation(probe_workqueue_creation, NULL);
- if (ret)
- goto no_execution;
-
- ret = register_trace_workqueue_destruction(probe_workqueue_destruction, NULL);
- if (ret)
- goto no_creation;
-
- return 0;
-
-no_creation:
- unregister_trace_workqueue_creation(probe_workqueue_creation, NULL);
-no_execution:
- unregister_trace_workqueue_execution(probe_workqueue_execution, NULL);
-no_insertion:
- unregister_trace_workqueue_insertion(probe_workqueue_insertion, NULL);
-out:
- pr_warning("trace_workqueue: unable to trace workqueues\n");
-
- return 1;
-}
-early_initcall(trace_workqueue_early_init);
--
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.