On Thu, Jun 25 2026, Chenghao Duan wrote: > This patch adds support for preserving eventfd file descriptors across > kexec live updates using the Live Update Orchestrator (LUO) framework. > Userspace applications using eventfd for event notification can now > maintain their state across kernel updates. > > Preserved State: > The following properties of the eventfd are preserved across kexec: > - Counter Value: The current 64-bit counter value, including any pending > events that have been signaled but not yet consumed by readers. > - File Flags: The creation flags (EFD_SEMAPHORE, EFD_CLOEXEC, EFD_NONBLOCK) > are preserved. > > Non-Preserved State: > - File Descriptor Number: The eventfd will be assigned a new fd number > in the target process after restore. > - Wait Queue State: Any processes blocked on read() operations will be > woken up and need to re-establish their blocking state. > - All other internal state is reset to default. > > Changes: > - fs/eventfd.c: Add eventfd_luo_get_state() to safely read eventfd state > (count and flags), and eventfd_create() helper function. > - fs/eventfd_luo.c: New file implementing LUO file operations: > preserve, freeze, unpreserve, retrieve, and finish callbacks. > - include/linux/eventfd.h: Export new functions. > - include/linux/kho/abi/eventfd.h: Define the ABI contract with > eventfd_luo_ser structure for serialization.
Why do you need to preserve this? Why don't you create a fresh one after kexec? You just preserve the counter, which looks pretty much useless. You can just as well open a new eventfd after kexec and set the counter value if you care about it. [...] -- Regards, Pratyush Yadav
