From: Steven Rostedt <rostedt@goodmis.org>
To: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, Roman Gushchin <guro@fb.com>,
Hillf Danton <hdanton@sina.com>, Michal Hocko <mhocko@suse.com>,
Matthew Wilcox <willy@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Thomas Garnier <thgarnie@google.com>,
Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>,
Joel Fernandes <joelaf@google.com>,
Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH v3 4/4] mm/vmap: move BUG_ON() check to the unlink_va()
Date: Mon, 27 May 2019 08:59:27 -0400 [thread overview]
Message-ID: <20190527085927.19152502@gandalf.local.home> (raw)
In-Reply-To: <20190527093842.10701-5-urezki@gmail.com>
On Mon, 27 May 2019 11:38:42 +0200
"Uladzislau Rezki (Sony)" <urezki@gmail.com> wrote:
> Move the BUG_ON()/RB_EMPTY_NODE() check under unlink_va()
> function, it means if an empty node gets freed it is a BUG
> thus is considered as faulty behaviour.
Can we switch it to a WARN_ON(). We are trying to remove all BUG_ON()s.
If a user wants to crash on warning, there's a sysctl for that. But
crashing the system can make it hard to debug. Especially if it is hit
by someone without a serial console, and the machine just hangs in X.
That is very annoying.
With a WARN_ON, you at least get a chance to see the crash dump.
-- Steve
>
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> ---
> mm/vmalloc.c | 24 +++++++++---------------
> 1 file changed, 9 insertions(+), 15 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 371aba9a4bf1..340959b81228 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -533,20 +533,16 @@ link_va(struct vmap_area *va, struct rb_root *root,
> static __always_inline void
> unlink_va(struct vmap_area *va, struct rb_root *root)
> {
> - /*
> - * During merging a VA node can be empty, therefore
> - * not linked with the tree nor list. Just check it.
> - */
> - if (!RB_EMPTY_NODE(&va->rb_node)) {
> - if (root == &free_vmap_area_root)
> - rb_erase_augmented(&va->rb_node,
> - root, &free_vmap_area_rb_augment_cb);
> - else
> - rb_erase(&va->rb_node, root);
> + BUG_ON(RB_EMPTY_NODE(&va->rb_node));
>
> - list_del(&va->list);
> - RB_CLEAR_NODE(&va->rb_node);
> - }
> + if (root == &free_vmap_area_root)
> + rb_erase_augmented(&va->rb_node,
> + root, &free_vmap_area_rb_augment_cb);
> + else
> + rb_erase(&va->rb_node, root);
> +
> + list_del(&va->list);
> + RB_CLEAR_NODE(&va->rb_node);
> }
>
> #if DEBUG_AUGMENT_PROPAGATE_CHECK
> @@ -1187,8 +1183,6 @@ EXPORT_SYMBOL_GPL(unregister_vmap_purge_notifier);
>
> static void __free_vmap_area(struct vmap_area *va)
> {
> - BUG_ON(RB_EMPTY_NODE(&va->rb_node));
> -
> /*
> * Remove from the busy tree/list.
> */
next prev parent reply other threads:[~2019-05-27 12:59 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-27 9:38 [PATCH v3 0/4] Some cleanups for the KVA/vmalloc Uladzislau Rezki (Sony)
2019-05-27 9:38 ` [PATCH v3 1/4] mm/vmap: remove "node" argument Uladzislau Rezki (Sony)
2019-05-28 22:33 ` Roman Gushchin
2019-05-27 9:38 ` [PATCH v3 2/4] mm/vmap: preload a CPU with one object for split purpose Uladzislau Rezki (Sony)
2019-05-28 22:42 ` Roman Gushchin
2019-05-29 14:27 ` Uladzislau Rezki
2019-05-29 16:34 ` Roman Gushchin
2019-06-03 17:53 ` Uladzislau Rezki
2019-06-03 20:53 ` Uladzislau Rezki
2019-06-03 21:06 ` Roman Gushchin
2019-05-27 9:38 ` [PATCH v3 3/4] mm/vmap: get rid of one single unlink_va() when merge Uladzislau Rezki (Sony)
2019-05-28 22:45 ` Roman Gushchin
2019-05-27 9:38 ` [PATCH v3 4/4] mm/vmap: move BUG_ON() check to the unlink_va() Uladzislau Rezki (Sony)
2019-05-27 12:59 ` Steven Rostedt [this message]
2019-05-27 14:02 ` Uladzislau Rezki
2019-05-28 22:50 ` Roman Gushchin
2019-05-29 13:58 ` Uladzislau Rezki
2019-05-29 16:26 ` Roman Gushchin
2019-06-03 17:35 ` Uladzislau Rezki
2019-06-03 20:30 ` Roman Gushchin
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