tools/virtio/asm/barrier.h

File Facts

System

Linux kernel

Corpus path

tools/virtio/asm/barrier.h

Extension

.h

Size

1128 bytes

Lines

33

Domain

Support Tooling And Documentation

Bucket

tools

Inferred role

Support Tooling And Documentation: implementation source

Status

source implementation candidate

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

• stdlib.h

Detected Declarations

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

Annotated Snippet

#include <stdlib.h>
#if defined(__i386__) || defined(__x86_64__)
#define barrier() asm volatile("" ::: "memory")
#define virt_mb() __sync_synchronize()
#define virt_rmb() barrier()
#define virt_wmb() barrier()
/* Atomic store should be enough, but gcc generates worse code in that case. */
#define virt_store_mb(var, value)  do { \
	typeof(var) virt_store_mb_value = (value); \
	__atomic_exchange(&(var), &virt_store_mb_value, &virt_store_mb_value, \
			  __ATOMIC_SEQ_CST); \
	barrier(); \
} while (0);
/* Weak barriers should be used. If not - it's a bug */
# define mb() abort()
# define dma_rmb() abort()
# define dma_wmb() abort()
#elif defined(__aarch64__)
#define dmb(opt) asm volatile("dmb " #opt : : : "memory")
#define virt_mb() __sync_synchronize()
#define virt_rmb() dmb(ishld)
#define virt_wmb() dmb(ishst)
#define virt_store_mb(var, value)  do { WRITE_ONCE(var, value); dmb(ish); } while (0)
/* Weak barriers should be used. If not - it's a bug */
# define mb() abort()
# define dma_rmb() abort()
# define dma_wmb() abort()
#else
#error Please fill in barrier macros
#endif

Annotation

• Immediate include surface: `stdlib.h`.
• Atlas domain: Support Tooling And Documentation / tools.
• Implementation status: source implementation candidate.
• 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.