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Date: Mon, 30 Jan 2012 20:53:04 -0800 From: Arjan van de Ven <arjan@...radead.org> To: linux-kernel@...r.kernel.org Cc: mingo@...e.hu, x86@...nel.org, arjanvandeven@...il.com Subject: x86: clean up smpboot.c's use of udelay+schedule >From 9f8dd2b15ff19ad73ee0eb235b4fdde9277185e8 Mon Sep 17 00:00:00 2001 From: Arjan van de Ven <arjan@...ux.intel.com> Date: Mon, 30 Jan 2012 20:38:09 -0800 Subject: [PATCH] x86: clean up smpboot.c's use of udelay+schedule smpboot.c does a udelay() followed by a schedule(); to yield the CPU to other threads. This comes from the time when the kernel did not yet have usleep_*() style APIs... ... nowadays, the kernel can do better than this, and this patch replaces this code sequence with a usleep_range(), so that the CPU is actually yielded for some real time. Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com> --- arch/x86/kernel/smpboot.c | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 66d250c..0b794c6 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -781,14 +781,13 @@ do_rest: for (timeout = 0; timeout < 50000; timeout++) { if (cpumask_test_cpu(cpu, cpu_callin_mask)) break; /* It has booted */ - udelay(100); /* * Allow other tasks to run while we wait for the * AP to come online. This also gives a chance * for the MTRR work(triggered by the AP coming online) * to be completed in the stop machine context. */ - schedule(); + usleep_range(100, 200); } if (cpumask_test_cpu(cpu, cpu_callin_mask)) -- 1.7.6.4 -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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