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mm/damon: simplify stop mechanism 

A 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 to it before termination.

Link: https://lkml.kernel.org/r/20211027130517.4404-1-changbin.du@gmail.com
Signed-off-by: Changbin Du <changbin.du@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Changbin Du 2021-11-05 13:48:22 -07:00 committed by Linus Torvalds
parent 0d16cfd46b
commit 0f91d13366
2 changed files with 15 additions and 37 deletions
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1
include/linux/damon.h
View File

@ -381,7 +381,6 @@ struct damon_ctx {
/* public: */
struct task_struct *kdamond;
bool kdamond_stop;
struct mutex kdamond_lock;
struct damon_primitive primitive;

51
mm/damon/core.c
View File

@ -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);