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Re: [PATCH 2/2] nilfs2: eliminate sparse warning - "context imbalance"



On Fri,  8 Oct 2010 22:37:28 +0900, Jiro SEKIBA wrote:
> insert sparse annotations to fix following sparse warning.
> 
> fs/nilfs2/segment.c:2681:3: warning: context imbalance in 'nilfs_segctor_kill_thread' - unexpected unlock
> 
> Signed-off-by: Jiro SEKIBA <jir@xxxxxxxxx>
> ---
>  fs/nilfs2/segment.c |   11 +++++++++++
>  1 files changed, 11 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
> index 172ad42..c64f6e4 100644
> --- a/fs/nilfs2/segment.c
> +++ b/fs/nilfs2/segment.c
> @@ -2677,12 +2677,23 @@ static void nilfs_segctor_kill_thread(struct nilfs_sc_info *sci)
>  {
>  	sci->sc_state |= NILFS_SEGCTOR_QUIT;
>  
> +	/* 
> +	 * nilfs_segctor_kill_thread is only called inside sc_state_lock lock.
> +	 * sparse doesn't detect the context and warn "unexpected unlock".
> +	 * This pretends to lock the sc_state_lock for sparse.
> +	 */
> +	__acquire(&sci->sc_state_lock);
>  	while (sci->sc_task) {
>  		wake_up(&sci->sc_wait_daemon);
>  		spin_unlock(&sci->sc_state_lock);
>  		wait_event(sci->sc_wait_task, sci->sc_task == NULL);
>  		spin_lock(&sci->sc_state_lock);
>  	}
> +	/*
> +	 * Pretending to lock sc_state_lock will cause "wrong count" warning.
> +	 * This pretends to unlock th sc_state_lock for sparse.
> +	 */
> +	__release(&sci->sc_state_lock);
>  }
>  
>  /*
> -- 
> 1.5.6.5

Thanks, but you don't have to insert __acquire() and __release() calls
in the function.  Just declare __releases() and __acquires() as below.

 static void nilfs_segctor_kill_thread(struct nilfs_sc_info *sci)
+       __releases(&sci->sc_state_lock)
+       __acquires(&sci->sc_state_lock)
 {

You can find this style of examples in other sites in the kernel.

Thanks,
Ryusuke Konishi
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