Documentation/litmus-tests/locking/RM-broken.litmus

File Facts

System

Linux kernel

Corpus path

Documentation/litmus-tests/locking/RM-broken.litmus

Extension

.litmus

Size

644 bytes

Lines

42

Domain

Support Tooling And Documentation

Bucket

Documentation

Inferred role

Support Tooling And Documentation: Documentation

Status

atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

• Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.
• Uses kernel synchronization; read lock ordering, sleepability, and interrupt context assumptions before translating.

Dependency Surface

• No C-style include directives detected by the generator.

Detected Declarations

• No top-level syscall, struct, function, initcall, or export declaration detected by the generator.

Annotated Snippet

C RM-broken

(*
 * Result: DEADLOCK
 *
 * This litmus test demonstrates that the old "roach motel" approach
 * to locking, where code can be freely moved into critical sections,
 * cannot be used in the Linux kernel.
 *)

{
	int x;
	atomic_t y;
}

P0(int *x, atomic_t *y, spinlock_t *lck)
{
	int r2;

	spin_lock(lck);
	r2 = atomic_inc_return(y);
	WRITE_ONCE(*x, 1);
	spin_unlock(lck);
}

P1(int *x, atomic_t *y, spinlock_t *lck)
{
	int r0;
	int r1;
	int r2;

	spin_lock(lck);
	r0 = READ_ONCE(*x);
	r1 = READ_ONCE(*x);
	r2 = atomic_inc_return(y);
	spin_unlock(lck);
}

locations [x;0:r2;1:r0;1:r1;1:r2]
filter (1:r0=0 /\ 1:r1=1)
exists (1:r2=1)

Annotation

• Atlas domain: Support Tooling And Documentation / Documentation.
• Implementation status: atlas-only.
• Synchronization appears in or near this file; preserve lock ordering, sleepability, and interrupt-context constraints.

Implementation Notes

• This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
• Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
• Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.