Re: [PATCH v2] livepatch: Fix idle cpu's tasks transition
From: Peter Zijlstra <peterz@infradead.org>
Date: 2021-09-21 17:43:34
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On Wed, Sep 15, 2021 at 04:18:01PM +0200, Vasily Gorbik wrote:
quoted hunk ↗ jump to hunk
diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c index 291b857a6e20..2846a879f2dc 100644 --- a/kernel/livepatch/transition.c +++ b/kernel/livepatch/transition.c@@ -278,6 +278,8 @@ static int klp_check_stack(struct task_struct *task, char *err_buf) * Try to safely switch a task to the target patch state. If it's currently * running, or it's sleeping on a to-be-patched or to-be-unpatched function, or * if the stack is unreliable, return false. + * + * Idle tasks are switched in the main loop when running. */ static bool klp_try_switch_task(struct task_struct *task) {@@ -308,6 +310,12 @@ static bool klp_try_switch_task(struct task_struct *task) rq = task_rq_lock(task, &flags); if (task_running(rq, task) && task != current) { + /* + * Idle task might stay running for a long time. Switch them + * in the main loop. + */ + if (is_idle_task(task)) + resched_curr(rq); snprintf(err_buf, STACK_ERR_BUF_SIZE, "%s: %s:%d is running\n", __func__, task->comm, task->pid);
So 'recently' we grew try_invoke_on_locked_down_task() (yes, that's a crap name), and I'm thinking this code is very similar to that. So perhaps we re-use that. Perhaps have func() > 0 imply resched. I'll have a play...