Initial skeleton of in-memory locks

Signed-off-by: Matthew Heon <matthew.heon@gmail.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/libpod/lock/shm_lock.h b/libpod/lock/shm_lock.h
new file mode 100644
index 000000000..6988789dd
--- /dev/null
+++ b/libpod/lock/shm_lock.h
@@ -0,0 +1,43 @@
+#ifndef shm_locks_h_
+#define shm_locks_h_
+
+#include <semaphore.h>
+#include <stdint.h>
+
+// Magic number to ensure we open the right SHM segment
+#define MAGIC 0xA5A5
+
+// Name of the SHM
+#define SHM_NAME "/libpod_lock"
+
+// Type for our bitmaps
+typedef uint32_t bitmap_t;
+
+// bitmap size
+#define BITMAP_SIZE (sizeof(bitmap_t) * 8)
+
+// Struct to hold a single bitmap and associated locks
+typedef struct lock_group {
+  bitmap_t bitmap;
+  sem_t    locks[BITMAP_SIZE];
+} lock_group_t;
+
+// Struct to hold our SHM locks
+typedef struct shm_struct {
+  uint16_t     magic;
+  sem_t        segment_lock;
+  uint32_t     num_bitmaps;
+  uint32_t     num_locks;
+  lock_group_t locks[];
+} shm_struct_t;
+
+size_t compute_shm_size(uint32_t num_bitmaps);
+shm_struct_t *setup_lock_shm(uint32_t num_locks);
+shm_struct_t *open_lock_shm(uint32_t num_locks);
+int32_t close_lock_shm(shm_struct_t *shm);
+int64_t allocate_semaphore(shm_struct_t *shm);
+int32_t deallocate_semaphore(shm_struct_t *shm, uint32_t sem_index);
+int32_t lock_semaphore(shm_struct_t *shm, uint32_t sem_index);
+int32_t unlock_semaphore(shm_struct_t *shm, uint32_t sem_index);
+
+#endif