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| author |   Jann Horn <jannh@google.com> | 2020-03-05 23:06:57 +0100 |
|---|---|---|
| committer |   Peter Zijlstra <peterz@infradead.org> | 2020-04-30 20:14:38 +0200 |
| commit | 586b58cac8b4683eb58a1446fbc399de18974e40 (patch) | |
| tree | a31aa2ff43c541f2ee7d098369379effb2ffffe4 /kernel/exit.c | |
| parent | sched/fair: Simplify the code of should_we_balance() (diff) | |
| download | linux-dev-586b58cac8b4683eb58a1446fbc399de18974e40.tar.xz linux-dev-586b58cac8b4683eb58a1446fbc399de18974e40.zip | |
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
Diffstat (limited to 'kernel/exit.c')
| -rw-r--r-- | kernel/exit.c | 25 |
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); |