Unconditional guard destructors have dead NULL checks. The lock operation in
the constructor would crash before the destructor ever runs with NULL.
- Patches 1-2 prepare guards that legitimately handle NULL.
- Patch 3 adds __nonnull() to guard constructors for compile-time enforcement.
- Patch 4 removes the dead checks.
As compiled by GCC-11 with defconfig on top of the locking/core:
Total: Before=23889980, After=23834334, chg -0.23%
Changes in v4:
- Re-worded commit message paragraph about nonnull "compiler-enforced
verification" (Miguel Ojeda).
- Fixed GCC documentation link for nonnull() attribute (Miguel Ojeda).
- Placed nonnull() before nonstring() in
include/linux/compiler_attributes.h (Miguel Ojeda).
- Picked up tags, where appropriate.
Changes in v3:
- Audited usages of DEFINE_GUARD(), __DEFINE_UNLOCK_GUARD() and
DEFINE_LOCK_GUARD_1() to make sure NULL check removal will work correctly
(Peter Zijlstra).
- Moved NULL check into irqdesc_lock unlock expression (Peter Zijlstra).
- Added compiler-enforced nonnull() check for guard constructors.
- Converted nvdimm_bus guard to class.
Changes in v2:
- Expand commit message with detailed reasoning, why the proposed
change is correct.
- Rebase on top of locking/core.
v3: https://lore.kernel.org/all/cover.1779116497.git.d@ilvokhin.com/
v2: https://lore.kernel.org/all/20260512071510.92451-1-d@ilvokhin.com/
v1: https://lore.kernel.org/all/20260427165037.205337-1-d@ilvokhin.com/
See also [1] for relevant discussion.
[1]: https://lore.kernel.org/all/afCS4d4YccQFtvpi@shell.ilvokhin.com/
Dmitry Ilvokhin (4):
nvdimm: Convert nvdimm_bus guard to class
genirq: Move NULL check into irqdesc_lock guard unlock expression
cleanup: Annotate guard constructors with __nonnull()
cleanup: Remove NULL check from unconditional guards
drivers/nvdimm/nd.h | 7 +++++--
include/linux/cleanup.h | 8 +++++---
include/linux/compiler_attributes.h | 6 ++++++
kernel/irq/internals.h | 2 +-
4 files changed, 17 insertions(+), 6 deletions(-)
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2.53.0-Meta