On Wed, 25 Sep 2024 08:59:04 -0500 "Serge E. Hallyn" <serge@xxxxxxxxxx> wrote: > On Wed, Sep 25, 2024 at 01:06:10PM +0200, Alice Ryhl wrote: > > On Tue, Sep 24, 2024 at 9:45 PM Serge E. Hallyn <serge@xxxxxxxxxx> wrote: > > > > > > On Sun, Sep 15, 2024 at 02:31:27PM +0000, Alice Ryhl wrote: > > > > This introduces a new marker type for types that shouldn't be thread > > > > safe. By adding a field of this type to a struct, it becomes non-Send > > > > and non-Sync, which means that it cannot be accessed in any way from > > > > threads other than the one it was created on. > > > > > > > > This is useful for APIs that require globals such as `current` to remain > > > > constant while the value exists. > > > > > > > > We update two existing users in the Kernel to use this helper: > > > > > > > > * `Task::current()` - moving the return type of this value to a > > > > different thread would not be safe as you can no longer be guaranteed > > > > that the `current` pointer remains valid. > > > > * Lock guards. Mutexes and spinlocks should be unlocked on the same > > > > thread as where they were locked, so we enforce this using the Send > > > > trait. > > > > > > Hi, > > > > > > this sounds useful, however from kernel side when I think thread-safe, > > > I think must not be used across a sleep. Would something like ThreadLocked > > > or LockedToThread make sense? > > > > Hmm, those names seem pretty similar to the current name to me? > > Seems very different to me: > > If @foo is not threadsafe, it may be global or be usable by many > threads, but must be locked to one thread during access. > > What you're describing here is (iiuc) that @foo must only be used > by one particular thread. "locked to one thread during access" means it might be `Send` but not `!Sync`. What Alice has here is something is neither `Send` nor `Sync`, so I think the `NotThreadSafe` is a good name here because it cancels both guarantees. Best, Gary
