Re: [PATCH v5 04/13] ACPI: extlog: Defer CXL protocol error handling to avoid lock inversion

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Missing IRQ disable in work registration functions causes spinlock-in-IRQ deadlock with hardirq context.
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commit 5baac18b0ad945081ea20f4dc8b72f0c31c675a3
Author: Dave Jiang <dave.jiang@intel.com>

ACPI: extlog: Defer CXL protocol error handling to avoid lock inversion

This commit fixes a lock inversion between the MCE notifier chain rwsem
and the PCI device_lock by deferring CXL protocol error handling to a
workqueue. It exports cxl_cper_post_prot_err() from the GHES driver to
be used by the extlog driver.

Link: https://lore.kernel.org/linux-cxl/20260709165457.8BA181F000E9@smtp.kernel.org/

> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> index 3236a3ce79d6b..a382aabf9835e 100644
> --- a/drivers/acpi/apei/ghes.c
> +++ b/drivers/acpi/apei/ghes.c

[ ... ]

> @@ -777,6 +777,7 @@ static void cxl_cper_post_prot_err(struct cxl_cper_sec_prot_err *prot_err,
>  	schedule_work(cxl_cper_prot_err_work);
>  #endif
>  }
> +EXPORT_SYMBOL_FOR_MODULES(cxl_cper_post_prot_err, "acpi_extlog");
>  
>  int cxl_cper_register_prot_err_work(struct work_struct *work)
>  {

[Severity: High]
This is a pre-existing issue, but since this patch exports and expands the
usage of cxl_cper_post_prot_err(), could this lock lead to a hardirq
deadlock?

In cxl_cper_register_prot_err_work() and
cxl_cper_unregister_prot_err_work(), the lock is taken without disabling
interrupts:

    guard(spinlock)(&cxl_cper_prot_err_work_lock);

If a GHES interrupt arrives on the same CPU while this lock is held,
ghes_irq_func() will process the event and call cxl_cper_post_prot_err(),
which attempts to acquire the same lock:

    guard(spinlock_irqsave)(&cxl_cper_prot_err_work_lock);

Does this cause the IRQ handler to spin forever waiting for the lock held
by the interrupted process? A similar pattern appears to exist for
cxl_cper_work_lock in cxl_cper_register_work().

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Sashiko AI review · https://sashiko.dev/#/patchset/20260827203726.3027541-1-dave.jiang@intel.com?part=4