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Re: [PATCH v2 09/12] xen/trace: Minor code cleanup


  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Tue, 21 Sep 2021 13:03:54 +0200
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  • Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Ian Jackson <iwj@xxxxxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Dario Faggioli <dfaggioli@xxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Tue, 21 Sep 2021 11:04:06 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 20.09.2021 19:25, Andrew Cooper wrote:
>  * Delete trailing whitespace
>  * Replace an opencoded DIV_ROUND_UP()
>  * Drop bogus smp_rmb() - spin_lock_irqsave() has full smp_mb() semantics.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Like for v1: Largely
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
One remark:

> @@ -717,9 +713,6 @@ void __trace_var(u32 event, bool_t cycles, unsigned int 
> extra,
>      if ( !cpumask_test_cpu(smp_processor_id(), &tb_cpu_mask) )
>          return;
>  
> -    /* Read tb_init_done /before/ t_bufs. */
> -    smp_rmb();
> -
>      spin_lock_irqsave(&this_cpu(t_lock), flags);
>  
>      buf = this_cpu(t_bufs);

I wonder whether the comment wouldn't be helpful to move down here,
in of course a slightly edited form (going from /before/ to /after/).

Jan




 


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