kernel/linux.git - Linux kernel stable tree (mirror)

Age	Commit message (Collapse)	Author	Files	Lines
2019-08-20	powerpc/64: allow compiler to cache 'current'	Nicholas Piggin	1	-1/+2
	current may be cached by the compiler, so remove the volatile asm restriction. This results in better generated code, as well as being smaller and fewer dependent loads, it can avoid store-hit-load flushes like this one that shows up in irq_exit(): preempt_count_sub(HARDIRQ_OFFSET); if (!in_interrupt() && ...) Which ends up as: ((struct thread_info )current)->preempt_count -= HARDIRQ_OFFSET; if (((struct thread_info )current)->preempt_count ... Evaluating current twice presently means it has to be loaded twice, and here gcc happens to pick a different register each time, then preempt_count is accessed via that base register: 1058: ld r10,2392(r13) <-- current 105c: lwz r9,0(r10) <-- preempt_count 1060: addis r9,r9,-1 1064: stw r9,0(r10) <-- preempt_count 1068: ld r9,2392(r13) <-- current 106c: lwz r9,0(r9) <-- preempt_count 1070: rlwinm. r9,r9,0,11,23 1074: bne 1090 <irq_exit+0x60> This can frustrate store-hit-load detection heuristics and cause flushes. Allowing the compiler to cache current in a reigster with this patch results in the same base register being used for all accesses, which is more likely to be detected as an alias: 1058: ld r31,2392(r13) ... 1070: lwz r9,0(r31) 1074: addis r9,r9,-1 1078: stw r9,0(r31) 107c: lwz r9,0(r31) 1080: rlwinm. r9,r9,0,11,23 1084: bne 10a0 <irq_exit+0x60> Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20190612140317.24490-1-npiggin@gmail.com
2019-05-30	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152	Thomas Gleixner	1	-4/+1
	Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 3029 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Allison Randal <allison@lohutok.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2008-08-04	powerpc: Move include files to arch/powerpc/include/asm	Stephen Rothwell	1	-0/+40
	from include/asm-powerpc. This is the result of a mkdir arch/powerpc/include/asm git mv include/asm-powerpc/* arch/powerpc/include/asm Followed by a few documentation/comment fixups and a couple of places where <asm-powepc/...> was being used explicitly. Of the latter only one was outside the arch code and it is a driver only built for powerpc. Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Paul Mackerras <paulus@samba.org>