Commit 2ce02a86 authored Aug 24, 2020 by Jiang Biao Committed by Bjorn Helgaas Sep 17, 2020

PCI: Add schedule point in pci_read_config()

The PCI sysfs "config" file allows large reads, and the resulting PCI
config reads can take several milliseconds to complete.  Testing with the
cyclictest [1] benchmark showed 5ms+ latencies.

Add a schedule point in pci_read_config() to reduce the maximum latency.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/clrkwllms/rt-tests.git/

[bhelgaas: commit log]
Link: https://lore.kernel.org/r/20200824052025.48362-1-benbjiang@tencent.com


Reported-by: Bin Lai <robinlai@tencent.com>
Signed-off-by: Jiang Biao <benbjiang@tencent.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

parent d24e1245

drivers/pci/pci-sysfs.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -708,6 +708,7 @@ static ssize_t pci_read_config(struct file filp, struct kobject kobj,
		data[off - init_off + 3] = (val >> 24) & 0xff;
		off += 4;
		size -= 4;
		cond_resched();
		}

		if (size >= 2) {

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