Commit ac2a5539 authored May 13, 2014 by Yinghai Lu Committed by Thomas Gleixner Jun 04, 2014

x86: irq: Get correct available vectors for cpu disable



check_irq_vectors_for_cpu_disable() can overestimate the number of
available interrupt vectors, so the check for cpu down succeeds, but
the actual cpu removal fails.

It iterates from FIRST_EXTERNAL_VECTOR to NR_VECTORS, which is wrong
because the systems vectors are not taken into account.

Limit the search to first_system_vector instead of NR_VECTORS.

The second indicator for vector availability the used_vectors bitmap
is not taken into account at all. So system vectors,
e.g. IA32_SYSCALL_VECTOR (0x80) and IRQ_MOVE_CLEANUP_VECTOR (0x20),
are accounted as available.

Add a check for the used_vectors bitmap and do not account vectors
which are marked there.

[ tglx: Simplified code. Rewrote changelog and code comments. ]

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Acked-by: Prarit Bhargava <prarit@redhat.com>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Steven Rostedt (Red Hat) <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Elliott, Robert (Server Storage)" <Elliott@hp.com>
Cc: x86@kernel.org
Link: http://lkml.kernel.org/r/1400160305-17774-2-git-send-email-prarit@redhat.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

parent d2cfd310

arch/x86/kernel/irq.c

+12 −4

Original line number	Diff line number	Diff line
		@@ -17,6 +17,7 @@
		#include <asm/idle.h>
		#include <asm/mce.h>
		#include <asm/hw_irq.h>
		#include <asm/desc.h>

		#define CREATE_TRACE_POINTS
		#include <asm/trace/irq_vectors.h>
		@@ -334,9 +335,16 @@ int check_irq_vectors_for_cpu_disable(void)
		for_each_online_cpu(cpu) {
		if (cpu == this_cpu)
		continue;
		for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS;
		vector++) {
		if (per_cpu(vector_irq, cpu)[vector] < 0)
		/*
		* We scan from FIRST_EXTERNAL_VECTOR to first system
		* vector. If the vector is marked in the used vectors
		* bitmap or an irq is assigned to it, we don't count
		* it as available.
		*/
		for (vector = FIRST_EXTERNAL_VECTOR;
		vector < first_system_vector; vector++) {
		if (!test_bit(vector, used_vectors) &&
		per_cpu(vector_irq, cpu)[vector] < 0)
		count++;
		}
		}

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