Commit-ID: bcc4a62a73cb65327d7268fbfa3a786d603f52dc Gitweb: https://git.kernel.org/tip/bcc4a62a73cb65327d7268fbfa3a786d603f52dc Author: Andy Lutomirski <l...@kernel.org> AuthorDate: Thu, 4 Oct 2018 14:44:45 -0700 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Fri, 5 Oct 2018 10:12:18 +0200
x86/vdso: Document vgtod_ts better After reading do_hres() and do_course() and scratching my head a bit, I figured out why the arithmetic is strange. Document it. Signed-off-by: Andy Lutomirski <l...@kernel.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/f66f53d81150bbad47d7b282c9207a71a3ce1c16.1538689401.git.l...@kernel.org Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/include/asm/vgtod.h | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h index d17b092b9f1b..69d05c6d47f5 100644 --- a/arch/x86/include/asm/vgtod.h +++ b/arch/x86/include/asm/vgtod.h @@ -13,6 +13,15 @@ typedef u64 gtod_long_t; typedef unsigned long gtod_long_t; #endif +/* + * There is one of these objects in the vvar page for each + * vDSO-accelerated clockid. For high-resolution clocks, this encodes + * the time corresponding to vsyscall_gtod_data.cycle_last. For coarse + * clocks, this encodes the actual time. + * + * To confuse the reader, for high-resolution clocks, nsec is left-shifted + * by vsyscall_gtod_data.shift. + */ struct vgtod_ts { u64 sec; u64 nsec;
