linux-kernel - Re: [PATCH v2] PCI: vmd: Fix spinlock usage on config access for RT kernel

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Message-Id: <20241219005538.9125-1-ryotkkr98@gmail.com>
Date: Thu, 19 Dec 2024 09:55:38 +0900
From: Ryo Takakura <ryotkkr98@...il.com>
To: kbusch@...nel.org
Cc: bhelgaas@...gle.com,
	bigeasy@...utronix.de,
	jonathan.derrick@...ux.dev,
	kw@...ux.com,
	lgoncalv@...hat.com,
	linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org,
	linux-rt-devel@...ts.linux.dev,
	lpieralisi@...nel.org,
	manivannan.sadhasivam@...aro.org,
	nirmal.patel@...ux.intel.com,
	robh@...nel.org,
	rostedt@...dmis.org
Subject: Re: [PATCH v2] PCI: vmd: Fix spinlock usage on config access for RT kernel

Hi Keith,

On Wed, 18 Dec 2024 08:36:54 -0700, Keith Busch wrote:
>> @@ -385,13 +384,11 @@ static int vmd_pci_read(struct pci_bus *bus, unsigned int devfn, int reg,
>>  {
>>  	struct vmd_dev *vmd = vmd_from_bus(bus);
>>  	void __iomem *addr = vmd_cfg_addr(vmd, bus, devfn, reg, len);
>> -	unsigned long flags;
>>  	int ret = 0;
>>  
>>  	if (!addr)
>>  		return -EFAULT;
>>  
>> -	spin_lock_irqsave(&vmd->cfg_lock, flags);
>>  	switch (len) {
>>  	case 1:
>>  		*value = readb(addr);
>
>There's a comment above this function explaining the need for the lock,
>which doesn't make a lot of sense after this patch.

Thanks for pointing it out! It slipped my mind.
I'll leave it as it is for the next patch :)

Sincerely,
Ryo Takakura