Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the callback

From	okaya@codeaurora.org
Newsgroups	linux.kernel
Subject	Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the callback
Date	2016-08-08 14:20 +0200
Message-ID	<s3RHb-1ii-3@gated-at.bofh.it> (permalink)
References	(2 earlier) <rYkVz-4mo-3@gated-at.bofh.it> <rYP3k-5F3-15@gated-at.bofh.it> <s2qg1-IE-1@gated-at.bofh.it> <s2rF7-1SU-11@gated-at.bofh.it> <s3OpX-7tU-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 2016-08-08 04:51, Vinod Koul wrote:
> 
>> This patch is needed to fix a race condition as the commit message 
>> describes.
>> The callback is called before returning the descriptor back to free 
>> pool.
>> 
>> If the client calls free resources, the descriptor that was not 
>> returned to free pool gets lost due
>> to race condition.
> 
> Hmmm, if you have txn's pending and client wants to free up, shouldn't
> the pending txn's be cleaned up? Sound like a different bug to me..
> 
> So if I submit 5 txn's and now want to freeup, will you still leak
> descriptors? Doesn't sound as right behaviour to me.
> 

If free is called from the callback, current code will leak the current 
descriptor where free was called. It will release the other 4.

Because of ordering problem, descriptor is not in the active, pending or 
free pool.

I check pending txn by looking at active and queued lists when free is 
called.

After the callback, I put the descriptor back to free pool. At this 
moment, it is already too late.

>> I'll refactor the code after Dave's change for passing the error code 
>> while calling the
>> callback. That will be a different patch anyhow.
> 
> Yes the error reporting is different

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Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Vinod Koul <vinod.koul@intel.com> - 2016-08-04 14:50 +0200
  Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Sinan Kaya <okaya@codeaurora.org> - 2016-08-04 16:20 +0200
    Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-08-04 16:50 +0200
      Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-08-04 17:40 +0200
        Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Sinan Kaya <okaya@codeaurora.org> - 2016-08-04 18:10 +0200
          Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Lars-Peter Clausen <lars@metafoo.de> - 2016-08-04 18:20 +0200
            Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the callback Robert Jarzmik <robert.jarzmik@free.fr> - 2016-08-05 08:40 +0200
              Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Lars-Peter Clausen <lars@metafoo.de> - 2016-08-05 10:40 +0200
                Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Sinan Kaya <okaya@codeaurora.org> - 2016-08-05 17:20 +0200
        Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Lars-Peter Clausen <lars@metafoo.de> - 2016-08-04 18:10 +0200
          Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Vinod Koul <vinod.koul@intel.com> - 2016-08-08 11:10 +0200
            Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Lars-Peter Clausen <lars@metafoo.de> - 2016-08-08 14:30 +0200
              Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Vinod Koul <vinod.koul@intel.com> - 2016-08-10 20:50 +0200
      Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Sinan Kaya <okaya@codeaurora.org> - 2016-08-04 17:40 +0200
        Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Vinod Koul <vinod.koul@intel.com> - 2016-08-08 11:00 +0200
          Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Sinan Kaya <okaya@codeaurora.org> - 2016-08-08 16:50 +0200
            Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Vinod Koul <vinod.koul@intel.com> - 2016-08-10 21:00 +0200
              Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Sinan Kaya <okaya@codeaurora.org> - 2016-08-10 22:50 +0200
    Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback Vinod Koul <vinod.koul@intel.com> - 2016-08-08 10:50 +0200
      Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the  callback okaya@codeaurora.org - 2016-08-08 14:20 +0200

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