Oleg has pointed out that can simplify both oom_adj_{read,write} and
oom_score_adj_{read,write} even further and drop the sighand lock. The
main purpose of the lock was to protect p->signal from going away but this
will not happen since
ea6d290ca34c ("signals: make task_struct->signal
immutable/refcountable").
The other role of the lock was to synchronize different writers,
especially those with CAP_SYS_RESOURCE. Introduce a mutex for this
purpose. Later patches will need this lock anyway.
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Link: http://lkml.kernel.org/r/1466426628-15074-3-git-send-email-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
char buffer[PROC_NUMBUF];
int oom_adj = OOM_ADJUST_MIN;
size_t len;
char buffer[PROC_NUMBUF];
int oom_adj = OOM_ADJUST_MIN;
size_t len;
if (!task)
return -ESRCH;
if (!task)
return -ESRCH;
- if (lock_task_sighand(task, &flags)) {
- if (task->signal->oom_score_adj == OOM_SCORE_ADJ_MAX)
- oom_adj = OOM_ADJUST_MAX;
- else
- oom_adj = (task->signal->oom_score_adj * -OOM_DISABLE) /
- OOM_SCORE_ADJ_MAX;
- unlock_task_sighand(task, &flags);
- }
+ if (task->signal->oom_score_adj == OOM_SCORE_ADJ_MAX)
+ oom_adj = OOM_ADJUST_MAX;
+ else
+ oom_adj = (task->signal->oom_score_adj * -OOM_DISABLE) /
+ OOM_SCORE_ADJ_MAX;
put_task_struct(task);
len = snprintf(buffer, sizeof(buffer), "%d\n", oom_adj);
return simple_read_from_buffer(buf, count, ppos, buffer, len);
}
put_task_struct(task);
len = snprintf(buffer, sizeof(buffer), "%d\n", oom_adj);
return simple_read_from_buffer(buf, count, ppos, buffer, len);
}
+static DEFINE_MUTEX(oom_adj_mutex);
+
/*
* /proc/pid/oom_adj exists solely for backwards compatibility with previous
* kernels. The effective policy is defined by oom_score_adj, which has a
/*
* /proc/pid/oom_adj exists solely for backwards compatibility with previous
* kernels. The effective policy is defined by oom_score_adj, which has a
struct task_struct *task;
char buffer[PROC_NUMBUF];
int oom_adj;
struct task_struct *task;
char buffer[PROC_NUMBUF];
int oom_adj;
int err;
memset(buffer, 0, sizeof(buffer));
int err;
memset(buffer, 0, sizeof(buffer));
- if (!lock_task_sighand(task, &flags)) {
- err = -ESRCH;
- goto err_put_task;
- }
-
/*
* Scale /proc/pid/oom_score_adj appropriately ensuring that a maximum
* value is always attainable.
/*
* Scale /proc/pid/oom_score_adj appropriately ensuring that a maximum
* value is always attainable.
else
oom_adj = (oom_adj * OOM_SCORE_ADJ_MAX) / -OOM_DISABLE;
else
oom_adj = (oom_adj * OOM_SCORE_ADJ_MAX) / -OOM_DISABLE;
+ mutex_lock(&oom_adj_mutex);
if (oom_adj < task->signal->oom_score_adj &&
!capable(CAP_SYS_RESOURCE)) {
err = -EACCES;
if (oom_adj < task->signal->oom_score_adj &&
!capable(CAP_SYS_RESOURCE)) {
err = -EACCES;
task->signal->oom_score_adj = oom_adj;
trace_oom_score_adj_update(task);
task->signal->oom_score_adj = oom_adj;
trace_oom_score_adj_update(task);
-err_sighand:
- unlock_task_sighand(task, &flags);
-err_put_task:
+err_unlock:
+ mutex_unlock(&oom_adj_mutex);
put_task_struct(task);
out:
return err < 0 ? err : count;
put_task_struct(task);
out:
return err < 0 ? err : count;
struct task_struct *task = get_proc_task(file_inode(file));
char buffer[PROC_NUMBUF];
short oom_score_adj = OOM_SCORE_ADJ_MIN;
struct task_struct *task = get_proc_task(file_inode(file));
char buffer[PROC_NUMBUF];
short oom_score_adj = OOM_SCORE_ADJ_MIN;
size_t len;
if (!task)
return -ESRCH;
size_t len;
if (!task)
return -ESRCH;
- if (lock_task_sighand(task, &flags)) {
- oom_score_adj = task->signal->oom_score_adj;
- unlock_task_sighand(task, &flags);
- }
+ oom_score_adj = task->signal->oom_score_adj;
put_task_struct(task);
len = snprintf(buffer, sizeof(buffer), "%hd\n", oom_score_adj);
return simple_read_from_buffer(buf, count, ppos, buffer, len);
put_task_struct(task);
len = snprintf(buffer, sizeof(buffer), "%hd\n", oom_score_adj);
return simple_read_from_buffer(buf, count, ppos, buffer, len);
{
struct task_struct *task;
char buffer[PROC_NUMBUF];
{
struct task_struct *task;
char buffer[PROC_NUMBUF];
int oom_score_adj;
int err;
int oom_score_adj;
int err;
- if (!lock_task_sighand(task, &flags)) {
- err = -ESRCH;
- goto err_put_task;
- }
-
+ mutex_lock(&oom_adj_mutex);
if ((short)oom_score_adj < task->signal->oom_score_adj_min &&
!capable(CAP_SYS_RESOURCE)) {
err = -EACCES;
if ((short)oom_score_adj < task->signal->oom_score_adj_min &&
!capable(CAP_SYS_RESOURCE)) {
err = -EACCES;
}
task->signal->oom_score_adj = (short)oom_score_adj;
if (has_capability_noaudit(current, CAP_SYS_RESOURCE))
task->signal->oom_score_adj_min = (short)oom_score_adj;
}
task->signal->oom_score_adj = (short)oom_score_adj;
if (has_capability_noaudit(current, CAP_SYS_RESOURCE))
task->signal->oom_score_adj_min = (short)oom_score_adj;
trace_oom_score_adj_update(task);
trace_oom_score_adj_update(task);
-err_sighand:
- unlock_task_sighand(task, &flags);
-err_put_task:
+err_unlock:
+ mutex_unlock(&oom_adj_mutex);
put_task_struct(task);
out:
return err < 0 ? err : count;
put_task_struct(task);
out:
return err < 0 ? err : count;