On Sun, May 25, 2025 at 10:07:56PM +0200, Rasmus Villemoes wrote: > On Thu, May 22 2025, Tom Rini <tr...@konsulko.com> wrote: > > > On Wed, May 07, 2025 at 02:12:42PM +0200, Rasmus Villemoes wrote: > > > >> While looking through list.h, I saw that the regular list_* helpers > >> (and one of the hlist_* ones) still contain the prefetch() that was > >> removed in linux 14 years ago. It doesn't do anything, but makes the > >> macros harder to read, so get rid of it, and the fallback, no-op > >> definition that they relied on. That requires removing a few uses > >> outside list.h as well. > >> > >> checkpatch warns about some whitespace issues in list.h, but as I've > >> copied whole kerneldoc+#define blocks directly from the linux kernel, > >> I think it's better to just accept that so that we don't introduce > >> needless diffs. The "macro argument reuse" arguments should also be > >> ignored, as e.g. the "member" arguments are obviously always just bare > >> identifiers, and the "pos" arguments must be assigned to multiple > >> times. > >> > >> Rasmus Villemoes (4): > >> linux/list.h: drop use of prefetch() > >> treewide: drop no-op prefetch() calls > >> mips: drop unused prefetch code and logic > >> linux/list.h: drop fallback definition of prefetch() > >> > >> arch/mips/include/asm/processor.h | 16 ----- > >> drivers/net/mvpp2.c | 1 - > >> drivers/net/octeontx/nicvf_main.c | 2 - > >> drivers/usb/gadget/at91_udc.c | 1 - > >> drivers/usb/musb-new/musb_core.c | 2 - > >> include/linux/list.h | 104 +++++++++++++++++------------- > >> 6 files changed, 59 insertions(+), 67 deletions(-) > > > > Unfortunately this leads to build problems on lots of platforms: > > https://source.denx.de/u-boot/u-boot/-/jobs/1141951 > > :( so we've been relying on that prefetch() laundering away the > volatile. > > Which really begs the question: Why, exactly, is it that gd even has > that volatile qualifier in the first place?
The answer is likely early 2000s GCC. > I'm 98% certain that we could drop that and get better code generation > and avoid a ton of places where we cast away that volatile which > shouldn't really be there anyway. It would be a good thing to experiment with now and maybe try for real in a near-future merge window. -- Tom
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