From: Omar Sandoval <osandov@osandov.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Alexey Dobriyan <adobriyan@gmail.com>,
Eric Biederman <ebiederm@xmission.com>,
James Morse <james.morse@arm.com>,
Bhupesh Sharma <bhsharma@redhat.com>,
kernel-team@fb.com
Subject: Re: [PATCH v2 1/7] proc/kcore: don't grab lock for kclist_add()
Date: Tue, 17 Jul 2018 20:19:14 -0700 [thread overview]
Message-ID: <20180718031914.GA29351@vader> (raw)
In-Reply-To: <20180717193504.1d76fb1a43d0c8687d969143@linux-foundation.org>
On Tue, Jul 17, 2018 at 07:35:04PM -0700, Andrew Morton wrote:
> On Thu, 12 Jul 2018 17:09:33 -0700 Omar Sandoval <osandov@osandov.com> wrote:
>
> > From: Omar Sandoval <osandov@fb.com>
> >
> > kclist_add() is only called at init time, so there's no point in
> > grabbing any locks. We're also going to replace the rwlock with a rwsem,
> > which we don't want to try grabbing during early boot.
> >
> > ...
> >
> > --- a/fs/proc/kcore.c
> > +++ b/fs/proc/kcore.c
> > @@ -62,6 +62,7 @@ static LIST_HEAD(kclist_head);
> > static DEFINE_RWLOCK(kclist_lock);
> > static int kcore_need_update = 1;
> >
> > +/* This doesn't grab kclist_lock, so it should only be used at init time. */
> > void
> > kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
> > {
> > @@ -69,9 +70,7 @@ kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
> > new->size = size;
> > new->type = type;
> >
> > - write_lock(&kclist_lock);
> > list_add_tail(&new->list, &kclist_head);
> > - write_unlock(&kclist_lock);
> > }
>
> So we can mark kclist_add() as __init, yes?
Yes, thanks, I'll add that in v2.
> That way we save a scrap of ram and if someone starts calling
> kclist_add() from non-__init code we get a build-time warning.
>
> --- a/fs/proc/kcore.c~proc-kcore-dont-grab-lock-for-kclist_add-fix
> +++ a/fs/proc/kcore.c
> @@ -63,7 +63,7 @@ static DEFINE_RWLOCK(kclist_lock);
> static int kcore_need_update = 1;
>
> /* This doesn't grab kclist_lock, so it should only be used at init time. */
> -void
> +void __init
> kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
> {
> new->addr = (unsigned long)addr;
> --- a/include/linux/kcore.h~proc-kcore-dont-grab-lock-for-kclist_add-fix
> +++ a/include/linux/kcore.h
> @@ -35,7 +35,7 @@ struct vmcoredd_node {
> };
>
> #ifdef CONFIG_PROC_KCORE
> -extern void kclist_add(struct kcore_list *, void *, size_t, int type);
> +extern void __init kclist_add(struct kcore_list *, void *, size_t, int type);
> #else
> static inline
> void kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
>
>
next prev parent reply other threads:[~2018-07-18 3:19 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-13 0:09 [PATCH v2 0/7] /proc/kcore improvements Omar Sandoval
2018-07-13 0:09 ` [PATCH v2 1/7] proc/kcore: don't grab lock for kclist_add() Omar Sandoval
2018-07-18 2:35 ` Andrew Morton
2018-07-18 3:19 ` Omar Sandoval [this message]
2018-07-13 0:09 ` [PATCH v2 2/7] proc/kcore: replace kclist_lock rwlock with rwsem Omar Sandoval
2018-07-18 2:38 ` Andrew Morton
2018-07-18 3:24 ` Omar Sandoval
2018-07-18 3:27 ` Andrew Morton
2018-07-18 3:36 ` Omar Sandoval
2018-07-13 0:09 ` [PATCH v2 3/7] proc/kcore: fix memory hotplug vs multiple opens race Omar Sandoval
2018-07-13 0:09 ` [PATCH v2 4/7] proc/kcore: hold lock during read Omar Sandoval
2018-07-13 0:09 ` [PATCH v2 5/7] proc/kcore: clean up ELF header generation Omar Sandoval
2018-07-13 0:09 ` [PATCH v2 6/7] proc/kcore: optimize multiple page reads Omar Sandoval
2018-07-13 0:09 ` [PATCH v2 7/7] proc/kcore: add vmcoreinfo note to /proc/kcore Omar Sandoval
2018-07-18 2:44 ` Andrew Morton
2018-07-18 3:27 ` Omar Sandoval
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