lkml.org 
[lkml]   [2022]   [Jun]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH 2/2] ANDROID: cfi: free old cfi shadow asynchronously
Date
> Hi,
>
> On Thu, Jun 30, 2022 at 2:47 AM Haibo Li <haibo.li@mediatek.com> wrote:
> >
> > Currenly, it uses synchronize_rcu() to wait old rcu reader to go away
> > in update_shadow.In embedded platform like ARM CA7X, load_module
> > blocks 40~50ms in update_shadow.
> > When there are more than one hundred kernel modules, it blocks several
> > seconds.
> >
> > To accelerate load_module,change synchronize_rcu to call_rcu.
> >
> > Signed-off-by: Haibo Li <haibo.li@mediatek.com>
> > Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
>
> Thanks for the patch! Please drop ANDROID: from the subject line, that's only
> used in the Android kernel trees.
>
Thanks for the comment.I will change it in next patch.
> > kernel/cfi.c | 12 ++++++++++--
> > 1 file changed, 10 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/cfi.c b/kernel/cfi.c index
> > 456771c8e454..a4836d59ca27 100644
> > --- a/kernel/cfi.c
> > +++ b/kernel/cfi.c
> > @@ -43,6 +43,8 @@ typedef u16 shadow_t; struct cfi_shadow {
> > /* Page index for the beginning of the shadow */
> > unsigned long base;
> > + /* rcu to free old cfi_shadow asynchronously */
> > + struct rcu_head rcu;
> > /* An array of __cfi_check locations (as indices to the shadow) */
> > shadow_t shadow[1];
> > } __packed;
> > @@ -182,6 +184,13 @@ static void remove_module_from_shadow(struct
> cfi_shadow *s, struct module *mod,
> > }
> > }
> >
> > +static void _cfi_shadow_free_rcu(struct rcu_head *rcu)
>
> I think this can be simply renamed to free_shadow.
Thanks for the comment.I will change it in next patch.
>
> > +{
> > + struct cfi_shadow *old = container_of(rcu, struct cfi_shadow,
> > +rcu);
> > +
> > + vfree(old);
> > +}
> > +
> > typedef void (*update_shadow_fn)(struct cfi_shadow *, struct module *,
> > unsigned long min_addr, unsigned long
> > max_addr);
> >
> > @@ -211,11 +220,10 @@ static void update_shadow(struct module *mod,
> > unsigned long base_addr,
> >
> > rcu_assign_pointer(cfi_shadow, next);
> > mutex_unlock(&shadow_update_lock);
> > - synchronize_rcu();
> >
> > if (prev) {
> > set_memory_rw((unsigned long)prev, SHADOW_PAGES);
> > - vfree(prev);
> > + call_rcu(&prev->rcu, _cfi_shadow_free_rcu);
> > }
> > }
>
> It's probably better to keep the pages read-only until they're actually released.
> Can you move the set_memory_rw call to the new function?
>
Since call_rcu and rcu callbacks change members in &prev->rcu,the old pages need to be rw at first.


\
 
 \ /
  Last update: 2022-07-01 04:43    [W:0.143 / U:0.348 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site