linux-kernel - Re: [PATCH] android: binder: Disable preemption while holding the global binder lock

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Date:   Thu, 8 Sep 2016 19:46:52 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Todd Kjos <tkjos@...gle.com>
Cc:     Arve Hjønnevåg <arve@...roid.com>,
        Riley Andrews <riandrews@...roid.com>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] android: binder: Disable preemption while holding the
 global binder lock

On Thu, Sep 08, 2016 at 09:12:50AM -0700, Todd Kjos wrote:
> In Android systems, the display pipeline relies on low
> latency binder transactions and is therefore sensitive to
> delays caused by contention for the global binder lock.
> Jank is siginificantly reduced by disabling preemption
> while the global binder lock is held.
> 
> Originally-from: Riley Andrews <riandrews@...gle.com>

So should the "From: " line be Riley?  Did Riley sign off on this?

> Signed-off-by: Todd Kjos <tkjos@...gle.com>
> ---
>  drivers/android/binder.c | 194 +++++++++++++++++++++++++++++++++++------------
>  1 file changed, 146 insertions(+), 48 deletions(-)
> 
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 16288e7..c36e420 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -379,6 +379,7 @@ static int task_get_unused_fd_flags(struct
> binder_proc *proc, int flags)
>   struct files_struct *files = proc->files;
>   unsigned long rlim_cur;
>   unsigned long irqs;
> + int ret;
> 
>   if (files == NULL)
>   return -ESRCH;
> @@ -389,7 +390,11 @@ static int task_get_unused_fd_flags(struct
> binder_proc *proc, int flags)
>   rlim_cur = task_rlimit(proc->tsk, RLIMIT_NOFILE);
>   unlock_task_sighand(proc->tsk, &irqs);
> 
> - return __alloc_fd(files, 0, rlim_cur, flags);
> + preempt_enable_no_resched();
> + ret = __alloc_fd(files, 0, rlim_cur, flags);
> + preempt_disable();
> +
> + return ret;
>  }

Your tabs are all eaten and broke the patch, so it can't be applied :(

Can you try again?

thanks,

greg k-h