Re: [PATCH v4 04/13] ACPI: extlog: Defer CXL protocol error handling to avoid lock inversion

On Mon, 24 Aug 2026 10:49:27 -0700
Dave Jiang <[email protected]> wrote:

> extlog_print() calls cxl_cper_handle_prot_err() synchronously while the
> MCE notifier chain rwsem is held, and that path takes the PCI device_lock
> via guard(device)(). The probe path takes the two in the opposite order,
> holding device_lock while mce_register_decode_chain() takes the rwsem, so
> they can deadlock AB-BA.
> 
> ghes.c already avoids this by posting protocol errors to a kfifo and
> handling them from a workqueue via cxl_cper_post_prot_err(). Export that
> function and call it instead.
> 
> Declare it with the other CONFIG_ACPI_APEI_GHES exports rather than at the
> end of the header. No #else stub: ACPI_EXTLOG selects ACPI_APEI_GHES, so
> the only caller cannot exist without it.
> 
> Reported-by: [email protected]
> Closes: https://lore.kernel.org/linux-cxl/[email protected]/
> Reviewed-by: Alison Schofield <[email protected]>
> Reviewed-by: Shuai Xue <[email protected]>
> Assisted-by: Claude:claude-sonnet-4-6
> Signed-off-by: Dave Jiang <[email protected]>
Makes sense to standardize irrespective of all the other reasons!
Reviewed-by: Jonathan Cameron <[email protected]>