Re: [PATCH 2/5] arm/pci: Use official API to iterate over PCI buses
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From: Gerd Bayer <gbayer@linux.ibm.com>
Date: 2026-05-18 15:46:29
Also in:
linux-alpha, linux-arm-kernel, linux-pci, lkml
On Fri, 2026-05-15 at 16:22 +0200, Gerd Bayer wrote:
quoted hunk ↗ jump to hunk
Replace iterating over pci_root_buses with the official pci_find_next_bus() call provided by PCI core. This allows to make pci_root_buses private to PCI core. Signed-off-by: Gerd Bayer <gbayer@linux.ibm.com> --- arch/arm/kernel/bios32.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)diff --git a/arch/arm/kernel/bios32.c b/arch/arm/kernel/bios32.c index ac0e890510da..35642c9ba054 100644 --- a/arch/arm/kernel/bios32.c +++ b/arch/arm/kernel/bios32.c@@ -59,9 +59,9 @@ static void pcibios_bus_report_status(struct pci_bus *bus, u_int status_mask, in void pcibios_report_status(u_int status_mask, int warn) { - struct pci_bus *bus; + struct pci_bus *bus = NULL; - list_for_each_entry(bus, &pci_root_buses, node) + while ((bus = pci_find_next_bus(bus)) != NULL) pcibios_bus_report_status(bus, status_mask, warn); }
Hi Russell, Sashiko https://sashiko.dev/#/message/20260515145940.E85AAC2BCB0%40smtp.kernel.org reported:
Since pci_find_next_bus() unconditionally acquires the pci_bus_sem read-write
semaphore using down_read(), this introduces a blocking operation into that
atomic path:
dc21285_abort_irq() [hardirq context]
pcibios_report_status()
pci_find_next_bus()
down_read(&pci_bus_sem) [sleeps]
Does this path need an alternative approach to safely iterate over the buses
without taking a sleeping lock?IMHO, it looks like this entire pcibios_report_status() iterating over all PCI buses and all their devices would be better off if moved outside of the hardirq context? Or could pcibios_report_status() be converted to use for_each_pci_device()? Any suggestions welcome... Gerd