On 2024/02/21 3:27, Vlastimil Babka wrote: > I'm sure more such scenarios exist, Cc: Tetsuo who I recall was an expert on > this topic. "[PATCH v3 10/35] lib: code tagging framework" says that codetag_lock_module_list() calls down_read() (i.e. sleeping operation), and "[PATCH v3 31/35] lib: add memory allocations report in show_mem()" says that __show_mem() calls alloc_tags_show_mem_report() after kmalloc(GFP_ATOMIC) (i.e. non-sleeping operation) but alloc_tags_show_mem_report() calls down_read() via codetag_lock_module_list() !? If __show_mem() might be called from atomic context (e.g. kmalloc(GFP_ATOMIC)), this will be a sleep in atomic bug. If __show_mem() might be called while semaphore is held for write, this will be a read-lock after write-lock deadlock bug. Not the matter of whether to allocate buffer statically or dynamically. Please don't hold a lock when trying to report memory usage.
