From: Marco Elver <elver@google.com>
To: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: Baoquan He <bhe@redhat.com>, Jonathan Corbet <corbet@lwn.net>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
kexec@lists.infradead.org, linux-doc@vger.kernel.org,
kasan-dev@googlegroups.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/5] sched: unset panic_on_warn before calling panic()
Date: Fri, 28 Jan 2022 12:52:10 +0100 [thread overview]
Message-ID: <CANpmjNPYYAy2jy_U_c7QjTsco6f1Hk2q=HP34di4YRMgdKsa+g@mail.gmail.com> (raw)
In-Reply-To: <1643370145-26831-5-git-send-email-yangtiezhu@loongson.cn>
On Fri, 28 Jan 2022 at 12:42, Tiezhu Yang <yangtiezhu@loongson.cn> wrote:
>
> As done in the full WARN() handler, panic_on_warn needs to be cleared
> before calling panic() to avoid recursive panics.
>
> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
> ---
> kernel/sched/core.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 848eaa0..f5b0886 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5524,8 +5524,17 @@ static noinline void __schedule_bug(struct task_struct *prev)
> pr_err("Preemption disabled at:");
> print_ip_sym(KERN_ERR, preempt_disable_ip);
> }
> - if (panic_on_warn)
> +
> + if (panic_on_warn) {
> + /*
> + * This thread may hit another WARN() in the panic path.
> + * Resetting this prevents additional WARN() from panicking the
> + * system on this thread. Other threads are blocked by the
> + * panic_mutex in panic().
> + */
> + panic_on_warn = 0;
> panic("scheduling while atomic\n");
I agree this is worth fixing.
But: Why can't the "panic_on_warn = 0" just be moved inside panic(),
instead of copy-pasting this all over the place?
I may be missing something obvious why this hasn't been done before...
Thanks,
-- Marco
WARNING: multiple messages have this Message-ID (diff)
From: Marco Elver <elver@google.com>
To: kexec@lists.infradead.org
Subject: [PATCH 4/5] sched: unset panic_on_warn before calling panic()
Date: Fri, 28 Jan 2022 12:52:10 +0100 [thread overview]
Message-ID: <CANpmjNPYYAy2jy_U_c7QjTsco6f1Hk2q=HP34di4YRMgdKsa+g@mail.gmail.com> (raw)
In-Reply-To: <1643370145-26831-5-git-send-email-yangtiezhu@loongson.cn>
On Fri, 28 Jan 2022 at 12:42, Tiezhu Yang <yangtiezhu@loongson.cn> wrote:
>
> As done in the full WARN() handler, panic_on_warn needs to be cleared
> before calling panic() to avoid recursive panics.
>
> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
> ---
> kernel/sched/core.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 848eaa0..f5b0886 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5524,8 +5524,17 @@ static noinline void __schedule_bug(struct task_struct *prev)
> pr_err("Preemption disabled at:");
> print_ip_sym(KERN_ERR, preempt_disable_ip);
> }
> - if (panic_on_warn)
> +
> + if (panic_on_warn) {
> + /*
> + * This thread may hit another WARN() in the panic path.
> + * Resetting this prevents additional WARN() from panicking the
> + * system on this thread. Other threads are blocked by the
> + * panic_mutex in panic().
> + */
> + panic_on_warn = 0;
> panic("scheduling while atomic\n");
I agree this is worth fixing.
But: Why can't the "panic_on_warn = 0" just be moved inside panic(),
instead of copy-pasting this all over the place?
I may be missing something obvious why this hasn't been done before...
Thanks,
-- Marco
next prev parent reply other threads:[~2022-01-28 11:52 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-28 11:42 [PATCH 0/5] Update doc and fix some issues about kdump Tiezhu Yang
2022-01-28 11:42 ` Tiezhu Yang
2022-01-28 11:42 ` [PATCH 1/5] docs: kdump: update description about sysfs file system support Tiezhu Yang
2022-01-28 11:42 ` Tiezhu Yang
2022-01-30 2:10 ` Baoquan He
2022-01-30 2:10 ` Baoquan He
2022-01-28 11:42 ` [PATCH 2/5] docs: kdump: add scp sample to write out the dump file Tiezhu Yang
2022-01-28 11:42 ` Tiezhu Yang
2022-01-30 2:46 ` Baoquan He
2022-01-30 2:46 ` Baoquan He
2022-01-28 11:42 ` [PATCH 3/5] kcsan: unset panic_on_warn before calling panic() Tiezhu Yang
2022-01-28 11:42 ` Tiezhu Yang
2022-01-28 11:42 ` [PATCH 4/5] sched: " Tiezhu Yang
2022-01-28 11:42 ` Tiezhu Yang
2022-01-28 11:52 ` Marco Elver [this message]
2022-01-28 11:52 ` Marco Elver
2022-01-30 0:29 ` Tiezhu Yang
2022-01-30 0:29 ` Tiezhu Yang
2022-01-28 11:42 ` [PATCH 5/5] kfence: " Tiezhu Yang
2022-01-28 11:42 ` Tiezhu Yang
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