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| author | Thomas Weißschuh <thomas.weissschuh@linutronix.de> | 2026-03-04 08:49:06 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@kernel.org> | 2026-03-11 10:18:32 +0100 |
| commit | e13e3059dcc27b0b79603925e68200a148b2ef4e (patch) | |
| tree | 84febc48703ba4c8844d9a432e4df1954d157981 /arch/sparc/include/asm/vdso | |
| parent | d60c682bce3dce963d6cf8208ed60d586004ce49 (diff) | |
| download | lwn-e13e3059dcc27b0b79603925e68200a148b2ef4e.tar.gz lwn-e13e3059dcc27b0b79603925e68200a148b2ef4e.zip | |
sparc64: vdso: Introduce vdso/processor.h
The generic vDSO library expects a vdso/processor.h with an definition of
cpu_relax().
Split out cpu_relax() into this dedicated header.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Andreas Larsson <andreas@gaisler.com>
Reviewed-by: Andreas Larsson <andreas@gaisler.com>
Acked-by: Andreas Larsson <andreas@gaisler.com>
Link: https://patch.msgid.link/20260304-vdso-sparc64-generic-2-v6-9-d8eb3b0e1410@linutronix.de
Diffstat (limited to 'arch/sparc/include/asm/vdso')
| -rw-r--r-- | arch/sparc/include/asm/vdso/processor.h | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/arch/sparc/include/asm/vdso/processor.h b/arch/sparc/include/asm/vdso/processor.h new file mode 100644 index 000000000000..f7a9adc807f7 --- /dev/null +++ b/arch/sparc/include/asm/vdso/processor.h @@ -0,0 +1,41 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#ifndef _ASM_SPARC_VDSO_PROCESSOR_H +#define _ASM_SPARC_VDSO_PROCESSOR_H + +#include <linux/compiler.h> + +#if defined(__arch64__) + +/* Please see the commentary in asm/backoff.h for a description of + * what these instructions are doing and how they have been chosen. + * To make a long story short, we are trying to yield the current cpu + * strand during busy loops. + */ +#ifdef BUILD_VDSO +#define cpu_relax() asm volatile("\n99:\n\t" \ + "rd %%ccr, %%g0\n\t" \ + "rd %%ccr, %%g0\n\t" \ + "rd %%ccr, %%g0\n\t" \ + ::: "memory") +#else /* ! BUILD_VDSO */ +#define cpu_relax() asm volatile("\n99:\n\t" \ + "rd %%ccr, %%g0\n\t" \ + "rd %%ccr, %%g0\n\t" \ + "rd %%ccr, %%g0\n\t" \ + ".section .pause_3insn_patch,\"ax\"\n\t"\ + ".word 99b\n\t" \ + "wr %%g0, 128, %%asr27\n\t" \ + "nop\n\t" \ + "nop\n\t" \ + ".previous" \ + ::: "memory") +#endif /* BUILD_VDSO */ + +#else /* ! __arch64__ */ + +#define cpu_relax() barrier() + +#endif /* __arch64__ */ + +#endif /* _ASM_SPARC_VDSO_PROCESSOR_H */ |