On Sun Oct 11, 2026 at 1:52 PM BST, Thomas Weißschuh wrote: > Keeping the flags as part of the bitfield prevents the usage of > READ_ONCE()/WRITE_ONCE() with it. It also makes access from Rust > awkward. > > Make it a dedicated field. > > The new field will stay in the exact same location in the parent > structure.
Incorrect. > > No functional change. > > Signed-off-by: Thomas Weißschuh <[email protected]> > --- > include/linux/dynamic_debug.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h > index 0b34343df594..b1ff7c0e9a5f 100644 > --- a/include/linux/dynamic_debug.h > +++ b/include/linux/dynamic_debug.h > @@ -51,7 +51,7 @@ struct _ddebug { > #else > #define _DPRINTK_FLAGS_DEFAULT 0 > #endif > - u32 flags:8; > + u8 flags; This will change the layout of the struct, because it'll no longer be merged with the previous bitfields. The layout change can be avoided by make lineno + class explicitly take 3 bytes. Perhaps reduce lineno to u16 and have class be a standalone u8? No kernel source file (apart from pre-generated AMDGPU headers, which doesn't use dyndbg anyway) have more than 65535 lines. Alternatively we can just say the layout change is fine, as for 64-bit platforms with jump label patching, there's padding in the struct anyway so this doesn't grow the full struct size. Anyhow this needs to be noted explicitly. Best, Gary > #ifdef CONFIG_JUMP_LABEL > union { > struct static_key_true dd_key_true;
