linux-kernel - Re: [PATCH] PCI: hotplug: Use atomic_{fetch

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Date: Thu, 13 Jun 2024 10:51:34 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Uros Bizjak <ubizjak@...il.com>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>, Lukas Wunner <lukas@...ner.de>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: Re: [PATCH] PCI: hotplug: Use atomic_{fetch_}andnot() where
 appropriate

[+cc Lukas, Ilpo]

On Thu, Jun 13, 2024 at 10:24:24AM +0200, Uros Bizjak wrote:
> Use atomic_{fetch_}andnot(i, v) instead of atomic_{fetch_}and(~i, v).

If the purpose is to improve readability, let's mention that here.
Since this only touches pciehp, make the subject line "PCI: pciehp:
..." as was done in the past.

It looks like every use of atomic_and() uses a ~value and is hence a
candidate for a similar change, but I'm not sure that converting to
"andnot" and removing the explicit bitwise NOT is really a readability
benefit.

If it were named something like "atomic_clear_bits", I'd be totally in
favor since that's a little higher-level description, but that ship
has long since sailed.

But I don't really care and if this is the trend, I'm fine with this
if Lukas and Ilpo agree.

> No functional changes intended.
> 
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Signed-off-by: Uros Bizjak <ubizjak@...il.com>
> ---
>  drivers/pci/hotplug/pciehp_ctrl.c | 4 ++--
>  drivers/pci/hotplug/pciehp_hpc.c  | 8 ++++----
>  2 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
> index dcdbfcf404dd..7c775d9a6599 100644
> --- a/drivers/pci/hotplug/pciehp_ctrl.c
> +++ b/drivers/pci/hotplug/pciehp_ctrl.c
> @@ -121,8 +121,8 @@ static void remove_board(struct controller *ctrl, bool safe_removal)
>  		msleep(1000);
>  
>  		/* Ignore link or presence changes caused by power off */
> -		atomic_and(~(PCI_EXP_SLTSTA_DLLSC | PCI_EXP_SLTSTA_PDC),
> -			   &ctrl->pending_events);
> +		atomic_andnot(PCI_EXP_SLTSTA_DLLSC | PCI_EXP_SLTSTA_PDC,
> +			      &ctrl->pending_events);
>  	}
>  
>  	pciehp_set_indicators(ctrl, PCI_EXP_SLTCTL_PWR_IND_OFF,
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index b1d0a1b3917d..6d192f64ea19 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -307,8 +307,8 @@ int pciehp_check_link_status(struct controller *ctrl)
>  
>  	/* ignore link or presence changes up to this point */
>  	if (found)
> -		atomic_and(~(PCI_EXP_SLTSTA_DLLSC | PCI_EXP_SLTSTA_PDC),
> -			   &ctrl->pending_events);
> +		atomic_andnot(PCI_EXP_SLTSTA_DLLSC | PCI_EXP_SLTSTA_PDC,
> +			      &ctrl->pending_events);
>  
>  	pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
>  	ctrl_dbg(ctrl, "%s: lnk_status = %x\n", __func__, lnk_status);
> @@ -568,7 +568,7 @@ static void pciehp_ignore_dpc_link_change(struct controller *ctrl,
>  	 * Could be several if DPC triggered multiple times consecutively.
>  	 */
>  	synchronize_hardirq(irq);
> -	atomic_and(~PCI_EXP_SLTSTA_DLLSC, &ctrl->pending_events);
> +	atomic_andnot(PCI_EXP_SLTSTA_DLLSC, &ctrl->pending_events);
>  	if (pciehp_poll_mode)
>  		pcie_capability_write_word(pdev, PCI_EXP_SLTSTA,
>  					   PCI_EXP_SLTSTA_DLLSC);
> @@ -702,7 +702,7 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id)
>  	pci_config_pm_runtime_get(pdev);
>  
>  	/* rerun pciehp_isr() if the port was inaccessible on interrupt */
> -	if (atomic_fetch_and(~RERUN_ISR, &ctrl->pending_events) & RERUN_ISR) {
> +	if (atomic_fetch_andnot(RERUN_ISR, &ctrl->pending_events) & RERUN_ISR) {
>  		ret = pciehp_isr(irq, dev_id);
>  		enable_irq(irq);
>  		if (ret != IRQ_WAKE_THREAD)
> -- 
> 2.45.2
>