netdev - [Q] page_pool stats and 32bit architectures.

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Message-ID: <20250213093925.x_ggH1aj@linutronix.de>
Date: Thu, 13 Feb 2025 10:39:25 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: netdev@...r.kernel.org
Cc: Joe Damato <jdamato@...tly.com>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	Ilias Apalodimas <ilias.apalodimas@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [Q] page_pool stats and 32bit architectures.

Hi,

The statistics counter (page_pool_{alloc|recycle}_stats) use u64 and
this_cpu_inc() + regular read.
This is okay on 64bit architectures but on 32bit architectures inc +
read is split into two operations. So the 32bit arch might observe a
wrong value if the lower 32bit part of the counter overflows before the
upper part is updated.
We can ignore this or switch to u64_stats_t.
Suggestions?

Sebastian