On Thu, Nov 28 2024 at 20:55, Waiman Long wrote:
On 11/28/24 8:06 PM, Waiman Long wrote:That's way more sane.
On 11/28/24 4:28 AM, Peter Zijlstra wrote:One idea that I current have is to add a emergency callback pointer to
On Wed, Nov 27, 2024 at 06:34:55PM -0500, Waiman Long wrote:According to the functional comment of nmi_shootdown_cpus(),
The __register_nmi_handler() function can be called in NMI context fromThis seems fundamentally insane. Why are we okay with this?
nmi_shootdown_cpus() leading to a lockdep splat like the following.
* nmi_shootdown_cpus() can only be invoked once. After the first
* invocation all other CPUs are stuck in crash_nmi_callback() and
* cannot respond to a second NMI.
That is why it has to insert the crash_nmi_callback() call with
register_nmi_handler() here in the NMI context. Changing this will
require a fundamental redesign of the way this shutdown process need
to be handled and I am not knowledgeable enough to do that. I will
certainly appreciate idea to handle it in a more graceful way.
the nmi_desc structure which, if set, has priority over the handlers in
the linked list and will be called first. In this way,
nmi_shootdown_cpus() can set the pointer to point to
crash_nmi_callback() without the need to take a lock and insert another
handler at the front of the list. Please let me know if this idea is
acceptable or not.