From: Linus Torvalds Date: Fri, 21 Aug 2009 16:23:57 +0000 (-0700) Subject: x86: don't send an IPI to the empty set of CPU's X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=83d349f35e1a;p=openwrt%2Fstaging%2Fblogic.git x86: don't send an IPI to the empty set of CPU's The default_send_IPI_mask_logical() function uses the "flat" APIC mode to send an IPI to a set of CPU's at once, but if that set happens to be empty, some older local APIC's will apparently be rather unhappy. So just warn if a caller gives us an empty mask, and ignore it. This fixes a regression in 2.6.30.x, due to commit 4595f9620 ("x86: change flush_tlb_others to take a const struct cpumask"), documented here: http://bugzilla.kernel.org/show_bug.cgi?id=13933 which causes a silent lock-up. It only seems to happen on PPro, P2, P3 and Athlon XP cores. Most developers sadly (or not so sadly, if you're a developer..) have more modern CPU's. Also, on x86-64 we don't use the flat APIC mode, so it would never trigger there even if the APIC didn't like sending an empty IPI mask. Reported-by: Pavel Vilim Reported-and-tested-by: Thomas Björnell Reported-and-tested-by: Martin Rogge Cc: Mike Travis Cc: Ingo Molnar Cc: stable@kernel.org Signed-off-by: Linus Torvalds --- diff --git a/arch/x86/kernel/apic/ipi.c b/arch/x86/kernel/apic/ipi.c index dbf5445727a9..6ef00ba4c886 100644 --- a/arch/x86/kernel/apic/ipi.c +++ b/arch/x86/kernel/apic/ipi.c @@ -106,6 +106,9 @@ void default_send_IPI_mask_logical(const struct cpumask *cpumask, int vector) unsigned long mask = cpumask_bits(cpumask)[0]; unsigned long flags; + if (WARN_ONCE(!mask, "empty IPI mask")) + return; + local_irq_save(flags); WARN_ON(mask & ~cpumask_bits(cpu_online_mask)[0]); __default_send_IPI_dest_field(mask, vector, apic->dest_logical);