linux-kernel - Re: [PATCH 2/4] swait: add the missing killable swaits

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Date:   Thu, 29 Jun 2017 14:54:02 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:     mfuzzey@...keon.com, ebiederm@...ssion.com,
        dmitry.torokhov@...il.com, wagi@...om.org, dwmw2@...radead.org,
        jewalt@...innovations.com, rafal@...ecki.pl,
        arend.vanspriel@...adcom.com, rjw@...ysocki.net,
        yi1.li@...ux.intel.com, atull@...nel.org, moritz.fischer@...us.com,
        pmladek@...e.com, johannes.berg@...el.com,
        emmanuel.grumbach@...el.com, luciano.coelho@...el.com,
        kvalo@...eaurora.org, luto@...nel.org,
        torvalds@...ux-foundation.org, keescook@...omium.org,
        takahiro.akashi@...aro.org, dhowells@...hat.com, pjones@...hat.com,
        hdegoede@...hat.com, alan@...ux.intel.com, tytso@....edu,
        mtk.manpages@...il.com, paul.gortmaker@...driver.com,
        mtosatti@...hat.com, mawilcox@...rosoft.com,
        linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "stable # 4 . 6" <stable@...r.kernel.org>
Subject: Re: [PATCH 2/4] swait: add the missing killable swaits

On Wed, Jun 14, 2017 at 03:20:15PM -0700, Luis R. Rodriguez wrote:
> Code in kernel which incorrectly used the non-killable variants could
> end up having waits killed improperly. The respective killable waits
> have been upstream for a while:
> 
>   o wait_for_completion_killable()
>   o wait_for_completion_killable_timeout()
> 
> swait has been upstream since v4.6. Older kernels have had the
> above variants in place for a long time.
> 
> Cc: stable <stable@...r.kernel.org> # 4.6
> Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
> ---
>  include/linux/swait.h | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/include/linux/swait.h b/include/linux/swait.h
> index c1f9c62a8a50..2c700694d50a 100644
> --- a/include/linux/swait.h
> +++ b/include/linux/swait.h
> @@ -169,4 +169,29 @@ do {									\
>  	__ret;								\
>  })
>  
> +#define __swait_event_killable(wq, condition)				\
> +	___swait_event(wq, condition, TASK_KILLABLE, 0, schedule())
> +
> +#define swait_event_killable(wq, condition)				\
> +({									\
> +	int __ret = 0;							\
> +	if (!(condition))						\
> +		__ret = __swait_event_killable(wq, condition);		\
> +	__ret;								\
> +})
> +
> +#define __swait_event_killable_timeout(wq, condition, timeout)		\
> +	___swait_event(wq, ___wait_cond_timeout(condition),		\
> +		       TASK_KILLABLE, timeout,				\
> +		       __ret = schedule_timeout(__ret))
> +
> +#define swait_event_killable_timeout(wq, condition, timeout)		\
> +({									\
> +	long __ret = timeout;						\
> +	if (!___wait_cond_timeout(condition))				\
> +		__ret = __swait_event_killable_timeout(wq,		\
> +						condition, timeout);	\
> +	__ret;								\
> +})
> +
>  #endif /* _LINUX_SWAIT_H */

Do you really still want to add these, now that we know we shouldn't be
using swait in "real" code? :)

thanks,

greg k-h