diff options
| -rw-r--r-- | src/backend/storage/buffer/localbuf.c | 13 | ||||
| -rw-r--r-- | src/include/storage/buf_internals.h | 6 |
2 files changed, 16 insertions, 3 deletions
diff --git a/src/backend/storage/buffer/localbuf.c b/src/backend/storage/buffer/localbuf.c index 68b402023a1..201ce2668fd 100644 --- a/src/backend/storage/buffer/localbuf.c +++ b/src/backend/storage/buffer/localbuf.c @@ -294,10 +294,14 @@ MarkLocalBufferDirty(Buffer buffer) bufHdr = GetLocalBufferDescriptor(bufid); - buf_state = pg_atomic_fetch_or_u32(&bufHdr->state, BM_DIRTY); + buf_state = pg_atomic_read_u32(&bufHdr->state); if (!(buf_state & BM_DIRTY)) pgBufferUsage.local_blks_dirtied++; + + buf_state |= BM_DIRTY; + + pg_atomic_write_u32(&bufHdr->state, buf_state); } /* @@ -431,6 +435,13 @@ InitLocalBuffers(void) * is -1.) */ buf->buf_id = -i - 2; + + /* + * Intentionally do not initialize the buffer's atomic variable + * (besides zeroing the underlying memory above). That way we get + * errors on platforms without atomics, if somebody (re-)introduces + * atomic operations for local buffers. + */ } /* Create the lookup hash table */ diff --git a/src/include/storage/buf_internals.h b/src/include/storage/buf_internals.h index f8f71255fdd..c9cae956a54 100644 --- a/src/include/storage/buf_internals.h +++ b/src/include/storage/buf_internals.h @@ -165,8 +165,10 @@ typedef struct buftag * wait_backend_pid and setting flag bit BM_PIN_COUNT_WAITER. At present, * there can be only one such waiter per buffer. * - * We use this same struct for local buffer headers, but the lock fields - * are not used and not all of the flag bits are useful either. + * We use this same struct for local buffer headers, but the locks are not + * used and not all of the flag bits are useful either. To avoid unnecessary + * overhead, manipulations of the state field should be done without actual + * atomic operations (i.e. only pg_atomic_read/write). * * Be careful to avoid increasing the size of the struct when adding or * reordering members. Keeping it below 64 bytes (the most common CPU |