Move to POSIX mutexes for SHM locks

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

1 files changed, 19 insertions, 16 deletions

diff --git a/libpod/lock/shm/shm_lock.h b/libpod/lock/shm/shm_lock.h
index 18bea47e9..8e7e23fb7 100644
--- a/libpod/lock/shm/shm_lock.h
+++ b/libpod/lock/shm/shm_lock.h
@@ -1,14 +1,11 @@
 #ifndef shm_locks_h_
 #define shm_locks_h_
 
-#include <semaphore.h>
+#include <pthread.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"
+#define MAGIC 0x87D1
 
 // Type for our bitmaps
 typedef uint32_t bitmap_t;
@@ -18,22 +15,28 @@ typedef uint32_t bitmap_t;
 
 // Struct to hold a single bitmap and associated locks
 typedef struct lock_group {
-  bitmap_t bitmap;
-  sem_t    locks[BITMAP_SIZE];
+  bitmap_t        bitmap;
+  pthread_mutex_t locks[BITMAP_SIZE];
 } lock_group_t;
 
-// Struct to hold our SHM locks
+// Struct to hold our SHM locks.
+// Unused is required to be 0 in the current implementation. If we ever make
+// changes to this structure in the future, this will be repurposed as a version
+// field.
 typedef struct shm_struct {
-  uint16_t     magic;
-  sem_t        segment_lock;
-  uint32_t     num_bitmaps;
-  uint32_t     num_locks;
-  lock_group_t locks[];
+  uint16_t        magic;
+  uint16_t        unused;
+  pthread_mutex_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, int *error_code);
-shm_struct_t *open_lock_shm(uint32_t num_locks, int *error_code);
+static size_t compute_shm_size(uint32_t num_bitmaps);
+static int take_mutex(pthread_mutex_t *mutex);
+static int release_mutex(pthread_mutex_t *mutex);
+shm_struct_t *setup_lock_shm(char *path, uint32_t num_locks, int *error_code);
+shm_struct_t *open_lock_shm(char *path, uint32_t num_locks, int *error_code);
 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);