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    Subject[Patch v4 2/3] PCI: Restrict probe functions to housekeeping CPUs
    Date
    From: Alex Belits <abelits@marvell.com>

    pci_call_probe() prevents the nesting of work_on_cpu() for a scenario
    where a VF device is probed from work_on_cpu() of the PF.

    Replace the cpumask used in pci_call_probe() from all online CPUs to only
    housekeeping CPUs. This is to ensure that there are no additional latency
    overheads caused due to the pinning of jobs on isolated CPUs.

    Signed-off-by: Alex Belits <abelits@marvell.com>
    Signed-off-by: Nitesh Narayan Lal <nitesh@redhat.com>
    Acked-by: Bjorn Helgaas <bhelgaas@google.com>
    Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
    ---
    drivers/pci/pci-driver.c | 5 ++++-
    1 file changed, 4 insertions(+), 1 deletion(-)

    diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
    index da6510af1221..449466f71040 100644
    --- a/drivers/pci/pci-driver.c
    +++ b/drivers/pci/pci-driver.c
    @@ -12,6 +12,7 @@
    #include <linux/string.h>
    #include <linux/slab.h>
    #include <linux/sched.h>
    +#include <linux/sched/isolation.h>
    #include <linux/cpu.h>
    #include <linux/pm_runtime.h>
    #include <linux/suspend.h>
    @@ -333,6 +334,7 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev,
    const struct pci_device_id *id)
    {
    int error, node, cpu;
    + int hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
    struct drv_dev_and_id ddi = { drv, dev, id };

    /*
    @@ -353,7 +355,8 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev,
    pci_physfn_is_probed(dev))
    cpu = nr_cpu_ids;
    else
    - cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask);
    + cpu = cpumask_any_and(cpumask_of_node(node),
    + housekeeping_cpumask(hk_flags));

    if (cpu < nr_cpu_ids)
    error = work_on_cpu(cpu, local_pci_probe, &ddi);
    --
    2.18.4
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