memcg: mm_update_next_owner: kill the "retry" logic

Add the new helper, try_to_set_owner(), which tries to update mm->owner
once we see c->mm == mm.  This way mm_update_next_owner() doesn't need to
restart the list_for_each_entry/for_each_process loops from the very
beginning if it races with exit/exec, it can just continue.

Unlike the current code, try_to_set_owner() re-checks tsk->mm == mm before
it drops tasklist_lock, so it doesn't need get/put_task_struct().

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Oleg Nesterov <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: Eric W. Biederman <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Jinliang Zheng <[email protected]>
Cc: Mateusz Guzik <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Tycho Andersen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions