linux-kernel - Re: [PATCH 1/2] staging: irda: Replace mdelay with usleep_range in stir421x_fw

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Message-ID: <20180411070742.GE10795@localhost>
Date:   Wed, 11 Apr 2018 09:07:42 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     samuel@...tiz.org, gregkh@...uxfoundation.org, davem@...emloft.net,
        johan@...nel.org, arvind.yadav.cs@...il.com,
        netdev@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] staging: irda: Replace mdelay with usleep_range in
 stir421x_fw_upload

On Wed, Apr 11, 2018 at 09:29:34AM +0800, Jia-Ju Bai wrote:
> stir421x_fw_upload() is never called in atomic context.
> 
> The call chain ending up at stir421x_fw_upload() is:
> [1] stir421x_fw_upload() <- stir421x_patch_device() <- irda_usb_probe()
> 
> irda_usb_probe() is set as ".probe" in struct usb_driver.
> This function is not called in atomic context.
> 
> Despite never getting called from atomic context, stir421x_fw_upload()
> calls mdelay() to busily wait.
> This is not necessary and can be replaced with usleep_range() to
> avoid busy waiting.
> 
> This is found by a static analysis tool named DCNS written by myself.
> And I also manually check it.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>

This all looks good (also note the call to usb_control_msg(), which may
sleep, just above the mdelay()).

Reviewed-by: Johan Hovold <johan@...nel.org>

Thanks,
Johan