[+cc Thomas Gleixner, author of dc186ad741c1] On Fri, Nov 18, 2022 at 09:20:38AM +0000, David Laight wrote: > > From: ira.weiny@xxxxxxxxx > > Sent: 18 November 2022 00:05 > > > > Work item initialization needs to be done with either > > INIT_WORK_ONSTACK() or INIT_WORK() depending on how the work item is > > allocated. > > > > The callers of pci_doe_submit_task() allocate struct pci_doe_task on the > > stack and pci_doe_submit_task() incorrectly used INIT_WORK(). > > > > Jonathan suggested creating doe task allocation macros such as > > DECLARE_CDAT_DOE_TASK_ONSTACK().[1] The issue with this is the work > > function is not known to the callers and must be initialized correctly. > > > > A follow up suggestion was to have an internal 'pci_doe_work' item > > allocated by pci_doe_submit_task().[2] This requires an allocation which > > could restrict the context where tasks are used. > > > > Another idea was to have an intermediate step to initialize the task > > struct with a new call.[3] This added a lot of complexity. > > > > Lukas pointed out that object_is_on_stack() is available to detect this > > automatically. > > > > Use object_is_on_stack() to determine the correct init work function to > > call. > > This is all a bit strange. > The 'onstack' flag is needed for the diagnostic check: > is_on_stack = object_is_on_stack(addr); > if (is_on_stack == onstack) > return; > pr_warn(...); > WARN_ON(1); > > So setting the flag to the location of the buffer just subverts the check. > It that is sane there ought to be a proper way to do it. If object_is_on_stack() is sufficient to check whether a struct is on the stack or not, why doesn't __init_work() use it to auto-detect whether to call debug_object_init_on_stack() or debug_object_init()? Forcing developers to use a specific initializer for something that can be auto-detected is akin to treating them like kids and telling them "You didn't say the magic word." What's the point? Thanks, Lukas
