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SubjectRe: [PATCH 7/9] x86/pci: Pass lockdep condition to pcm_mmcfg_list iterator (v1)
On Mon, Jul 15, 2019 at 10:37:03AM -0400, Joel Fernandes (Google) wrote:
> The pcm_mmcfg_list is traversed with list_for_each_entry_rcu without a
> reader-lock held, because the pci_mmcfg_lock is already held. Make this
> known to the list macro so that it fixes new lockdep warnings that
> trigger due to lockdep checks added to list_for_each_entry_rcu().
>
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>

Ingo takes care of most patches to this file, but FWIW,

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

I would personally prefer if you capitalized the subject to match the
"x86/PCI:" convention that's used fairly consistently in
arch/x86/pci/.

Also, I didn't apply this to be sure, but it looks like this might
make a line or two wider than 80 columns, which I would rewrap if I
were applying this.

> ---
> arch/x86/pci/mmconfig-shared.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/pci/mmconfig-shared.c b/arch/x86/pci/mmconfig-shared.c
> index 7389db538c30..6fa42e9c4e6f 100644
> --- a/arch/x86/pci/mmconfig-shared.c
> +++ b/arch/x86/pci/mmconfig-shared.c
> @@ -29,6 +29,7 @@
> static bool pci_mmcfg_running_state;
> static bool pci_mmcfg_arch_init_failed;
> static DEFINE_MUTEX(pci_mmcfg_lock);
> +#define pci_mmcfg_lock_held() lock_is_held(&(pci_mmcfg_lock).dep_map)
>
> LIST_HEAD(pci_mmcfg_list);
>
> @@ -54,7 +55,7 @@ static void list_add_sorted(struct pci_mmcfg_region *new)
> struct pci_mmcfg_region *cfg;
>
> /* keep list sorted by segment and starting bus number */
> - list_for_each_entry_rcu(cfg, &pci_mmcfg_list, list) {
> + list_for_each_entry_rcu(cfg, &pci_mmcfg_list, list, pci_mmcfg_lock_held()) {
> if (cfg->segment > new->segment ||
> (cfg->segment == new->segment &&
> cfg->start_bus >= new->start_bus)) {
> @@ -118,7 +119,7 @@ struct pci_mmcfg_region *pci_mmconfig_lookup(int segment, int bus)
> {
> struct pci_mmcfg_region *cfg;
>
> - list_for_each_entry_rcu(cfg, &pci_mmcfg_list, list)
> + list_for_each_entry_rcu(cfg, &pci_mmcfg_list, list, pci_mmcfg_lock_held())
> if (cfg->segment == segment &&
> cfg->start_bus <= bus && bus <= cfg->end_bus)
> return cfg;
> --
> 2.22.0.510.g264f2c817a-goog
>

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