Make L0 thread-safe (mostly).

1 files changed, 6 insertions, 0 deletions

diff --git a/kernel/include/paging.h b/kernel/include/paging.h
index 720d6b3..44014a2 100644
--- a/kernel/include/paging.h
+++ b/kernel/include/paging.h
@@ -19,6 +19,12 @@ uint32_t pd_get_frame(void* vaddr);		// get physical frame for virtual address
 int pd_map_page(void* vaddr, uint32_t frame_id, bool rw);		// returns nonzero on error
 void pd_unmap_page(void* vaddr);	// does nothing if page not mapped
 
+// Note on concurrency : we expect that multiple threads will not try to map/unmap
+// pages in the same region at the same time. It can nevertheless happen that
+// several threads try to map pages that belong to the same 4M-section, and in that
+// case both might require the allocation of a new PT at the same location. These
+// cases are well-handled (the pagedir_t type contains a mutex used for this)
+
 pagedir_t *create_pagedir();		// returns zero on error
 void delete_pagedir(pagedir_t *pd);