On Tue 30-08-22 09:30:26, Dan Carpenter wrote:
> Hello Michal Hocko,
>
> The patch e8fedfea3dea: "mm: reduce noise in show_mem for lowmem
> allocations" from Aug 23, 2022, leads to the following Smatch static
> checker warning:
>
> kernel/panic.c:190 panic_print_sys_info()
> warn: sleeping in atomic context
What is this warning saying?
> kernel/panic.c
> 175 static void panic_print_sys_info(bool console_flush)
> 176 {
> 177 if (console_flush) {
> 178 if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG)
> 179 console_flush_on_panic(CONSOLE_REPLAY_ALL);
> 180 return;
> 181 }
> 182
> 183 if (panic_print & PANIC_PRINT_ALL_CPU_BT)
> 184 trigger_all_cpu_backtrace();
> 185
> 186 if (panic_print & PANIC_PRINT_TASK_INFO)
> 187 show_state();
> 188
> 189 if (panic_print & PANIC_PRINT_MEM_INFO)
> --> 190 show_mem(0, NULL, GFP_HIGHUSER_MOVABLE);
> ^^^^^^^^^^^^^^^^^^^^
> This obviously seems very deliberate and a lot of weird stuff happens
> during panic(). But the panic() function disables preemption so
> shouldn't this be GFP_ATOMIC? GFP_HIGHUSER_MOVABLE has __GFP_RECLAIM
> and triggering swap during a panic seems bad.
This function shouldn't ever be allocating any memory. The flag is
solely to infer which memory zones should be displayed. It acts as a
filter. Is it possible that the checker misinterprets the parameter's
meaning?
--
Michal Hocko
SUSE Labs
