Re: [PATCH RFC 06/11] dyndbg: make _ddebug::flags its own field
flat view
From: "Gary Guo" <gary@garyguo.net>
Date: 2026-10-11 13:23:25
Also in:
driver-core, linux-kselftest, lkml, rust-for-linux
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.
quoted hunk ↗ jump to hunk
No functional change. Signed-off-by: Thomas Weißschuh <linux@weissschuh.net> --- 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;