Fix peer access test synchronization issue

Add missing device synchronization calls to ensure resident device
operations are complete before peer device accesses memory.

The test was failing because when dev0 accesses peer memory from dev1,
PatternGen only syncs dev0 (the accessing device) but not dev1 (the
resident device). This can cause synchronization issues where dev0
reads peer memory before dev1 has completed all operations.

Changes:
- Sync dev1 after IPC import (Test 1) to ensure import operations complete
- Sync dev1 after granting peer access (Test 3) before dev0 accesses
  peer memory

This follows CUDA best practices: when accessing peer memory, sync the
resident device to ensure its operations are complete before the peer
device reads the memory.

Fixes test failures on ARM64 with CUDA 13.2 RC025.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: rwgk

cuda_core/tests/memory_ipc/test_peer_access.py

@@ -94,6 +94,8 @@ def child_main(self, mr, buffer):
         # Test 1: Buffer accessible from resident device (dev1) - should always work
         dev1 = Device(1)
         dev1.set_current()
+        # Sync dev1 to ensure IPC import operations are complete
+        dev1.sync()
         PatternGen(dev1, NBYTES).verify_buffer(buffer, seed=False)
 
         # Test 2: Buffer NOT accessible from dev0 initially (peer access not preserved)
@@ -106,6 +108,9 @@ def child_main(self, mr, buffer):
         dev1.set_current()
         mr.peer_accessible_by = [0]
         assert mr.peer_accessible_by == (0,)
+        # Sync dev1 to ensure peer access setup and any pending operations are complete
+        # before dev0 accesses the peer memory
+        dev1.sync()
         dev0.set_current()
         PatternGen(dev0, NBYTES).verify_buffer(buffer, seed=False)