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Date: Tue, 26 Oct 2021 23:30:33 +0800
From: Changbin Du <changbin.du@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: SeongJae Park <sj@...nel.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, Changbin Du <changbin.du@...il.com>
Subject: [PATCH] mm/damon: simplify stop mechanism
An kernel thread can exit gracefully with kthread_stop(). So we don't need
a new flag 'kdamond_stop'. And to make sure the task struct is not freed
when accessing it, get task struct on start and put it on stop.
And since the return value of 'before_terminate' callback is never used,
we make it have no return value.
Signed-off-by: Changbin Du <changbin.du@...il.com>
---
include/linux/damon.h | 3 +--
mm/damon/core.c | 59 +++++++++++++------------------------------
mm/damon/dbgfs.c | 5 ++--
3 files changed, 20 insertions(+), 47 deletions(-)
diff --git a/include/linux/damon.h b/include/linux/damon.h
index a14b3cc54cab..041966786270 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -322,7 +322,7 @@ struct damon_callback {
int (*before_start)(struct damon_ctx *context);
int (*after_sampling)(struct damon_ctx *context);
int (*after_aggregation)(struct damon_ctx *context);
- int (*before_terminate)(struct damon_ctx *context);
+ void (*before_terminate)(struct damon_ctx *context);
};
/**
@@ -381,7 +381,6 @@ struct damon_ctx {
/* public: */
struct task_struct *kdamond;
- bool kdamond_stop;
struct mutex kdamond_lock;
struct damon_primitive primitive;
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 46a6afea3030..46401c56bfb2 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -390,17 +390,6 @@ static unsigned long damon_region_sz_limit(struct damon_ctx *ctx)
return sz;
}
-static bool damon_kdamond_running(struct damon_ctx *ctx)
-{
- bool running;
-
- mutex_lock(&ctx->kdamond_lock);
- running = ctx->kdamond != NULL;
- mutex_unlock(&ctx->kdamond_lock);
-
- return running;
-}
-
static int kdamond_fn(void *data);
/*
@@ -418,13 +407,13 @@ static int __damon_start(struct damon_ctx *ctx)
mutex_lock(&ctx->kdamond_lock);
if (!ctx->kdamond) {
err = 0;
- ctx->kdamond_stop = false;
ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond.%d",
nr_running_ctxs);
if (IS_ERR(ctx->kdamond)) {
err = PTR_ERR(ctx->kdamond);
ctx->kdamond = NULL;
- }
+ } else
+ get_task_struct(ctx->kdamond);
}
mutex_unlock(&ctx->kdamond_lock);
@@ -474,18 +463,18 @@ int damon_start(struct damon_ctx **ctxs, int nr_ctxs)
*/
static int __damon_stop(struct damon_ctx *ctx)
{
+ int ret = -EPERM;
+
mutex_lock(&ctx->kdamond_lock);
if (ctx->kdamond) {
- ctx->kdamond_stop = true;
- mutex_unlock(&ctx->kdamond_lock);
- while (damon_kdamond_running(ctx))
- usleep_range(ctx->sample_interval,
- ctx->sample_interval * 2);
- return 0;
+ kthread_stop(ctx->kdamond);
+ put_task_struct(ctx->kdamond);
+ ctx->kdamond = NULL;
+ ret = 0;
}
mutex_unlock(&ctx->kdamond_lock);
- return -EPERM;
+ return ret;
}
/**
@@ -925,12 +914,8 @@ static bool kdamond_need_update_primitive(struct damon_ctx *ctx)
static bool kdamond_need_stop(struct damon_ctx *ctx)
{
struct damon_target *t;
- bool stop;
- mutex_lock(&ctx->kdamond_lock);
- stop = ctx->kdamond_stop;
- mutex_unlock(&ctx->kdamond_lock);
- if (stop)
+ if (kthread_should_stop())
return true;
if (!ctx->primitive.target_valid)
@@ -1021,13 +1006,6 @@ static int kdamond_wait_activation(struct damon_ctx *ctx)
return -EBUSY;
}
-static void set_kdamond_stop(struct damon_ctx *ctx)
-{
- mutex_lock(&ctx->kdamond_lock);
- ctx->kdamond_stop = true;
- mutex_unlock(&ctx->kdamond_lock);
-}
-
/*
* The monitoring daemon that runs as a kernel thread
*/
@@ -1038,17 +1016,18 @@ static int kdamond_fn(void *data)
struct damon_region *r, *next;
unsigned int max_nr_accesses = 0;
unsigned long sz_limit = 0;
+ bool done = false;
pr_debug("kdamond (%d) starts\n", current->pid);
if (ctx->primitive.init)
ctx->primitive.init(ctx);
if (ctx->callback.before_start && ctx->callback.before_start(ctx))
- set_kdamond_stop(ctx);
+ done = true;
sz_limit = damon_region_sz_limit(ctx);
- while (!kdamond_need_stop(ctx)) {
+ while (!kdamond_need_stop(ctx) && !done) {
if (kdamond_wait_activation(ctx))
continue;
@@ -1056,7 +1035,7 @@ static int kdamond_fn(void *data)
ctx->primitive.prepare_access_checks(ctx);
if (ctx->callback.after_sampling &&
ctx->callback.after_sampling(ctx))
- set_kdamond_stop(ctx);
+ done = true;
usleep_range(ctx->sample_interval, ctx->sample_interval + 1);
@@ -1069,7 +1048,7 @@ static int kdamond_fn(void *data)
sz_limit);
if (ctx->callback.after_aggregation &&
ctx->callback.after_aggregation(ctx))
- set_kdamond_stop(ctx);
+ done = true;
kdamond_apply_schemes(ctx);
kdamond_reset_aggregated(ctx);
kdamond_split_regions(ctx);
@@ -1088,16 +1067,12 @@ static int kdamond_fn(void *data)
damon_destroy_region(r, t);
}
- if (ctx->callback.before_terminate &&
- ctx->callback.before_terminate(ctx))
- set_kdamond_stop(ctx);
+ if (ctx->callback.before_terminate)
+ ctx->callback.before_terminate(ctx);
if (ctx->primitive.cleanup)
ctx->primitive.cleanup(ctx);
pr_debug("kdamond (%d) finishes\n", current->pid);
- mutex_lock(&ctx->kdamond_lock);
- ctx->kdamond = NULL;
- mutex_unlock(&ctx->kdamond_lock);
mutex_lock(&damon_lock);
nr_running_ctxs--;
diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index befb27a29aab..eccc14b34901 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -645,18 +645,17 @@ static void dbgfs_fill_ctx_dir(struct dentry *dir, struct damon_ctx *ctx)
debugfs_create_file(file_names[i], 0600, dir, ctx, fops[i]);
}
-static int dbgfs_before_terminate(struct damon_ctx *ctx)
+static void dbgfs_before_terminate(struct damon_ctx *ctx)
{
struct damon_target *t, *next;
if (!targetid_is_pid(ctx))
- return 0;
+ return;
damon_for_each_target_safe(t, next, ctx) {
put_pid((struct pid *)t->id);
damon_destroy_target(t);
}
- return 0;
}
static struct damon_ctx *dbgfs_new_ctx(void)
--
2.32.0
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