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Date: Wed, 4 Dec 2013 08:46:27 -0800
From: Christoph Hellwig <hch@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, Tony Luck <tony.luck@intel.com>,
        Robert Richter <rric@kernel.org>, Bjorn Helgaas <bhelgaas@google.com>,
        Aaro Koskinen <aaro.koskinen@iki.fi>,
        David Daney <david.daney@cavium.com>
Cc: linux-kernel@vger.kernel.org
Subject: smp_call_function_single with wait=0 considered harmful
Message-ID: <20131204164627.GA27677@infradead.org>
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While doing my recent work on the generic smp function calls I noticed
that smp_call_function_single without the wait flag can't work, as
it allocates struct call_single_data on stack, and without the wait
flag will happily return before the IPI has been executed.

This affects the following callers:

  arch/ia64/kernel/mca.c:mca_cpu_callback()
  arch/ia64/kernel/smpboot.c:ia64_sync_itc()
  arch/x86/kernel/kvm.c:kvm_cpu_notify()
  arch/x86/oprofile/nmi_int.c:oprofile_cpu_notifier()
  arch/x86/pci/amd_bus.c:amd_cpu_notify()
  drivers/staging/octeon/ethernet-rx.c:cvm_oct_enable_one_cpu()
  kernel/stop_machine.c:stop_two_cpus()

It would be good to get these fixed so that we could remove the
parameter.  Either convert them to wait, or use a preallocated
call_single_data and __smp_call_function_single.

After that I'd like to remove the wait argument to prevent further
abuses.