linux-kernel - Re: [PATCH 0/4] ath10k: a few incorrect return handling fix-up

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Message-ID: <20141230182842.GA18361@opentech.at>
Date:	Tue, 30 Dec 2014 19:28:43 +0100
From:	Nicholas Mc Guire <der.herr@...r.at>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc:	Kalle Valo <kvalo@....qualcomm.com>,
	Michal Kazior <michal.kazior@...to.com>,
	Ben Greear <greearb@...delatech.com>,
	Chun-Yeow Yeoh <yeohchunyeow@...il.com>,
	Yanbo Li <yanbol@....qualcomm.com>, ath10k@...ts.infradead.org,
	linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] ath10k: a few incorrect return handling fix-up

On Tue, 30 Dec 2014, Sergei Shtylyov wrote:

> Hello.
>
> On 12/30/2014 03:20 PM, Nicholas Mc Guire wrote:
>
>> wait_for_completion_timeout does not return negative values so the tests
>> for <= 0 are not needed and the case differentiation in the error handling
>> path unnecessary.
>
>    I decided to verify your statement and I saw that it seems wrong.  
> do_wait_for_common() can return -ERESTARTSYS and the return value gets  
> returned by its callers unchanged.

the -ERESTARTSYS only can be returned if state matches but
wait_for_completion_timemout passes TASK_UNINTERRUPTIBLE
so signal_pending_state will return 0 and never negativ

my understanding of the callchain is:
wait_for_completion_timemout with TASK_UNINTERRUPTIBLE
  -> wait_for_common(...TASK_UNINTERRUPTIBLE)
    -> __wait_for_common(...TASK_UNINTERRUPTIBLE)
      -> do_wait_for_common(...TASK_UNINTERRUPTIBLE)
        -> signal_pending_state(TASK_UNINTERRUPTIBLE...)

static inline int signal_pending_state(long state, struct task_struct *p)
{
        if (!(state & (TASK_INTERRUPTIBLE | TASK_WAKEKILL)))
                return 0;

so wait_for_completion_timemout should return 0 or 1 only

>
>> patch was only compile tested x86_64_defconfig + CONFIG_ATH_CARDS=m
>> CONFIG_ATH10K=m
>
>> patch is against linux-next 3.19.0-rc1 -next-20141226
>
>    Rather patches. It would have been better to send one patch instead of 
> 4 patches with the same name.
>
sorry for that - I had split it into separate patches as it was
in different files - giving them the same name of course was a bit
brain-dead.

please do give it one more look - if the above argument is invalid
I apologize for the noise.


thx!
hofrat
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