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 reference of it before termination.
Signed-off-by: Changbin Du <[email protected]>
---
include/linux/damon.h | 1 -
mm/damon/core.c | 51 +++++++++++++------------------------------
2 files changed, 15 insertions(+), 37 deletions(-)
diff --git a/include/linux/damon.h b/include/linux/damon.h
index a14b3cc54cab..50c6eb0dee1f 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -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..f37c17b53814 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);
/*
@@ -418,7 +407,6 @@ 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)) {
@@ -474,13 +462,15 @@ int damon_start(struct damon_ctx **ctxs, int nr_ctxs)
*/
static int __damon_stop(struct damon_ctx *ctx)
{
+ struct task_struct *tsk;
+
mutex_lock(&ctx->kdamond_lock);
- if (ctx->kdamond) {
- ctx->kdamond_stop = true;
+ tsk = ctx->kdamond;
+ if (tsk) {
+ get_task_struct(tsk);
mutex_unlock(&ctx->kdamond_lock);
- while (damon_kdamond_running(ctx))
- usleep_range(ctx->sample_interval,
- ctx->sample_interval * 2);
+ kthread_stop(tsk);
+ put_task_struct(tsk);
return 0;
}
mutex_unlock(&ctx->kdamond_lock);
@@ -925,12 +915,8 @@ 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 +1007,6 @@ 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 +1017,18 @@ 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 +1036,7 @@ 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 +1049,7 @@ 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);
@@ -1088,9 +1068,8 @@ 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);
--
2.32.0
Thank you for this patch!
On Wed, 27 Oct 2021 21:05:17 +0800 Changbin Du <[email protected]> wrote:
> 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 reference of it before termination.
>
> Signed-off-by: Changbin Du <[email protected]>
Reviewed-by: SeongJae Park <[email protected]>
Thanks,
SJ
> ---
> include/linux/damon.h | 1 -
> mm/damon/core.c | 51 +++++++++++++------------------------------
> 2 files changed, 15 insertions(+), 37 deletions(-)
>
> diff --git a/include/linux/damon.h b/include/linux/damon.h
> index a14b3cc54cab..50c6eb0dee1f 100644
> --- a/include/linux/damon.h
> +++ b/include/linux/damon.h
> @@ -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..f37c17b53814 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);
>
> /*
> @@ -418,7 +407,6 @@ 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)) {
> @@ -474,13 +462,15 @@ int damon_start(struct damon_ctx **ctxs, int nr_ctxs)
> */
> static int __damon_stop(struct damon_ctx *ctx)
> {
> + struct task_struct *tsk;
> +
> mutex_lock(&ctx->kdamond_lock);
> - if (ctx->kdamond) {
> - ctx->kdamond_stop = true;
> + tsk = ctx->kdamond;
> + if (tsk) {
> + get_task_struct(tsk);
> mutex_unlock(&ctx->kdamond_lock);
> - while (damon_kdamond_running(ctx))
> - usleep_range(ctx->sample_interval,
> - ctx->sample_interval * 2);
> + kthread_stop(tsk);
> + put_task_struct(tsk);
> return 0;
> }
> mutex_unlock(&ctx->kdamond_lock);
> @@ -925,12 +915,8 @@ 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 +1007,6 @@ 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 +1017,18 @@ 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 +1036,7 @@ 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 +1049,7 @@ 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);
> @@ -1088,9 +1068,8 @@ 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);
>
> --
> 2.32.0
>