90 lines
3.2 KiB
Diff
90 lines
3.2 KiB
Diff
From: Thomas Gleixner <tglx@linutronix.de>
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Date: Wed, 12 Apr 2017 22:07:31 +0200
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Subject: [PATCH 05/13] powerpc/smp: Replace open coded task affinity logic
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.11/older/patches-4.11.8-rt5.tar.xz
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Init task invokes smp_ops->setup_cpu() from smp_cpus_done(). Init task can
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run on any online CPU at this point, but the setup_cpu() callback requires
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to be invoked on the boot CPU. This is achieved by temporarily setting the
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affinity of the calling user space thread to the requested CPU and reset it
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to the original affinity afterwards.
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That's racy vs. CPU hotplug and concurrent affinity settings for that
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thread resulting in code executing on the wrong CPU and overwriting the
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new affinity setting.
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That's actually not a problem in this context as neither CPU hotplug nor
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affinity settings can happen, but the access to task_struct::cpus_allowed
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is about to restricted.
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Replace it with a call to work_on_cpu_safe() which achieves the same result.
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Acked-by: Michael Ellerman <mpe@ellerman.id.au>
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Cc: Fenghua Yu <fenghua.yu@intel.com>
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Cc: Tony Luck <tony.luck@intel.com>
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Cc: Herbert Xu <herbert@gondor.apana.org.au>
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Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
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Cc: Peter Zijlstra <peterz@infradead.org>
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Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Cc: Sebastian Siewior <bigeasy@linutronix.de>
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Cc: Lai Jiangshan <jiangshanlai@gmail.com>
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Cc: Viresh Kumar <viresh.kumar@linaro.org>
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Cc: Tejun Heo <tj@kernel.org>
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Cc: Paul Mackerras <paulus@samba.org>
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Cc: linuxppc-dev@lists.ozlabs.org
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Cc: "David S. Miller" <davem@davemloft.net>
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Cc: Len Brown <lenb@kernel.org>
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Link: http://lkml.kernel.org/r/20170412201042.518053336@linutronix.de
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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arch/powerpc/kernel/smp.c | 26 +++++++++++---------------
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1 file changed, 11 insertions(+), 15 deletions(-)
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--- a/arch/powerpc/kernel/smp.c
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+++ b/arch/powerpc/kernel/smp.c
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@@ -787,24 +787,21 @@ static struct sched_domain_topology_leve
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{ NULL, },
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};
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-void __init smp_cpus_done(unsigned int max_cpus)
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+static __init long smp_setup_cpu_workfn(void *data __always_unused)
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{
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- cpumask_var_t old_mask;
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+ smp_ops->setup_cpu(boot_cpuid);
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+ return 0;
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+}
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- /* We want the setup_cpu() here to be called from CPU 0, but our
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- * init thread may have been "borrowed" by another CPU in the meantime
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- * se we pin us down to CPU 0 for a short while
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+void __init smp_cpus_done(unsigned int max_cpus)
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+{
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+ /*
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+ * We want the setup_cpu() here to be called on the boot CPU, but
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+ * init might run on any CPU, so make sure it's invoked on the boot
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+ * CPU.
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*/
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- alloc_cpumask_var(&old_mask, GFP_NOWAIT);
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- cpumask_copy(old_mask, ¤t->cpus_allowed);
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- set_cpus_allowed_ptr(current, cpumask_of(boot_cpuid));
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-
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if (smp_ops && smp_ops->setup_cpu)
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- smp_ops->setup_cpu(boot_cpuid);
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-
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- set_cpus_allowed_ptr(current, old_mask);
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-
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- free_cpumask_var(old_mask);
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+ work_on_cpu_safe(boot_cpuid, smp_setup_cpu_workfn, NULL);
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if (smp_ops && smp_ops->bringup_done)
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smp_ops->bringup_done();
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@@ -812,7 +809,6 @@ void __init smp_cpus_done(unsigned int m
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dump_numa_cpu_topology();
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set_sched_topology(powerpc_topology);
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-
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}
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#ifdef CONFIG_HOTPLUG_CPU
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