exit: Move preemption fixup up, move blocking operations down (586b58ca) · Commits · 戴 / test

With CONFIG_DEBUG_ATOMIC_SLEEP=y and CONFIG_CGROUPS=y, kernel oopses in non-preemptible context look untidy; after the main oops, the kernel prints a "sleeping function called from invalid context" report because exit_signals() -> cgroup_threadgroup_change_begin() -> percpu_down_read() can sleep, and that happens before the preempt_count_set(PREEMPT_ENABLED) fixup. It looks like the same thing applies to profile_task_exit() and kcov_task_exit(). Fix it by moving the preemption fixup up and the calls to profile_task_exit() and kcov_task_exit() down. Fixes: ("sched/core: Robustify preemption leak checks") Signed-off-by:

Jann Horn <jannh@google.com> Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200305220657.46800-1-jannh@google.com

kernel/exit.c

+16 −9

Original line number	Diff line number	Diff line
		@@ -708,8 +708,12 @@ void __noreturn do_exit(long code)
		struct task_struct *tsk = current;
		int group_dead;

		profile_task_exit(tsk);
		kcov_task_exit(tsk);
		/*
		* We can get here from a kernel oops, sometimes with preemption off.
		* Start by checking for critical errors.
		* Then fix up important state like USER_DS and preemption.
		* Then do everything else.
		*/

		WARN_ON(blk_needs_flush_plug(tsk));

		@@ -727,6 +731,16 @@ void __noreturn do_exit(long code)
		*/
		set_fs(USER_DS);

		if (unlikely(in_atomic())) {
		pr_info("note: %s[%d] exited with preempt_count %d\n",
		current->comm, task_pid_nr(current),
		preempt_count());
		preempt_count_set(PREEMPT_ENABLED);
		}

		profile_task_exit(tsk);
		kcov_task_exit(tsk);

		ptrace_event(PTRACE_EVENT_EXIT, code);

		validate_creds_for_do_exit(tsk);
		@@ -744,13 +758,6 @@ void __noreturn do_exit(long code)

		exit_signals(tsk); /* sets PF_EXITING */

		if (unlikely(in_atomic())) {
		pr_info("note: %s[%d] exited with preempt_count %d\n",
		current->comm, task_pid_nr(current),
		preempt_count());
		preempt_count_set(PREEMPT_ENABLED);
		}

		/* sync mm's RSS info before statistics gathering */
		if (tsk->mm)
		sync_mm_rss(tsk->mm);

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