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authorJann Horn <jannh@google.com>2020-03-05 23:06:57 +0100
committerPeter Zijlstra <peterz@infradead.org>2020-04-30 20:14:38 +0200
commit586b58cac8b4683eb58a1446fbc399de18974e40 (patch)
treea31aa2ff43c541f2ee7d098369379effb2ffffe4
parent64297f2b03cc7a6d0184a435f1b296beca1bedd1 (diff)
exit: Move preemption fixup up, move blocking operations down
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: 1dc0fffc48af ("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
-rw-r--r--kernel/exit.c25
1 files changed, 16 insertions, 9 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index ce2a75bc0ade..d56fe51bdf07 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -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);