linux-kernel - Re: [PATCH 1/2] pci: host: pci-hyperv: Replace GFP_ATOMIC with GFP_KERNEL in hv_pci

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Date:   Mon, 19 Mar 2018 11:38:50 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        bhelgaas@...gle.com, devel@...uxdriverproject.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 1/2] pci: host: pci-hyperv: Replace GFP_ATOMIC with
 GFP_KERNEL in hv_pci_onchannelcallback

On Sun, Mar 18, 2018 at 10:53:02PM +0800, Jia-Ju Bai wrote:
> hv_pci_onchannelcallback() is not called in atomic context.
> 
> The call chain ending up at hv_pci_onchannelcallback() is:
> [1] hv_pci_onchannelcallback() <- hv_pci_probe()
> hv_pci_probe() is only set as ".probe" in hv_driver 
> structure "hv_pci_drv".
> 

Your static analysis tool is faulty and apparently so is Smatch.

$ smdb function_ptrs hv_pci_onchannelcallback

Says it can't find a caller.  When I look for function pointers I get:

$ smdb function_ptr hv_pci_onchannelcallback
hv_pci_onchannelcallback =  'hv_pci_onchannelcallback' , 'vmbus_open param 5' , '(struct vmbus_channel)->onchannel_callback' , '__read_once_size param 0'

Anyway the call tree is:

vmbus_chan_sched() <-- takes rcu_read_lock();
-> vmbus_channel_isr()
   -> channel->onchannel_callback() -> which is hv_pci_onchannelcallback()

regards,
dan carpenter