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McKenney" , Tim Chen Subject: Re: [PATCH v8 -tip 24/26] sched: Move core-scheduler interfacing code to a new file Message-ID: <20201103025822.GA693892@google.com> References: <20201020014336.2076526-1-joel@joelfernandes.org> <20201020014336.2076526-25-joel@joelfernandes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 26, 2020 at 09:05:52AM +0800, Li, Aubrey wrote: [..] > > +int sched_core_share_tasks(struct task_struct *t1, struct task_struct *t2) > > +{ > > + struct sched_core_task_write_tag wr = {}; /* for stop machine. */ > > + bool sched_core_put_after_stopper = false; > > + unsigned long cookie; > > + int ret = -ENOMEM; > > + > > + mutex_lock(&sched_core_tasks_mutex); > > + > > + /* > > + * NOTE: sched_core_get() is done by sched_core_alloc_task_cookie() or > > + * sched_core_put_task_cookie(). However, sched_core_put() is done > > + * by this function *after* the stopper removes the tasks from the > > + * core queue, and not before. This is just to play it safe. > > + */ > > + if (t2 == NULL) { > > + if (t1->core_task_cookie) { > > + sched_core_put_task_cookie(t1->core_task_cookie); > > + sched_core_put_after_stopper = true; > > + wr.tasks[0] = t1; /* Keep wr.cookies[0] reset for t1. */ > > + } > > + } else if (t1 == t2) { > > + /* Assign a unique per-task cookie solely for t1. */ > > + > > + cookie = sched_core_alloc_task_cookie(); > > + if (!cookie) > > + goto out_unlock; > > + > > + if (t1->core_task_cookie) { > > + sched_core_put_task_cookie(t1->core_task_cookie); > > + sched_core_put_after_stopper = true; > > + } > > + wr.tasks[0] = t1; > > + wr.cookies[0] = cookie; > > + } else > > + /* > > + * t1 joining t2 > > + * CASE 1: > > + * before 0 0 > > + * after new cookie new cookie > > + * > > + * CASE 2: > > + * before X (non-zero) 0 > > + * after 0 0 > > + * > > + * CASE 3: > > + * before 0 X (non-zero) > > + * after X X > > + * > > + * CASE 4: > > + * before Y (non-zero) X (non-zero) > > + * after X X > > + */ > > + if (!t1->core_task_cookie && !t2->core_task_cookie) { > > + /* CASE 1. */ > > + cookie = sched_core_alloc_task_cookie(); > > + if (!cookie) > > + goto out_unlock; > > + > > + /* Add another reference for the other task. */ > > + if (!sched_core_get_task_cookie(cookie)) { > > + return -EINVAL; > > ret = -EINVAL; mutex is not released otherwise... Good find and will fix. Minor suggestion: Could you truncate your emails when replying? thanks, - Joel