On 10/11/19 8:15 PM, Sebastian Andrzej Siewior wrote:
On 2019-10-11 00:33:18 [+0200], Uladzislau Rezki (Sony) wrote:Get rid of preempt_disable() and preempt_enable() when the preload is done for splitting purpose. The reason is that calling spin_lock() with disabled preemtion is forbidden in CONFIG_PREEMPT_RT kernel. Therefore, we do not guarantee that a CPU is preloaded, instead we minimize the case when it is not with this change. For example i run the special test case that follows the preload pattern and path. 20 "unbind" threads run it and each does 1000000 allocations. Only 3.5 times among 1000000 a CPU was not preloaded. So it can happen but the number is negligible. V1 -> V2: - move __this_cpu_cmpxchg check when spin_lock is taken, as proposed by Andrew Morton - add more explanation in regard of preloading - adjust and move some comments Fixes: 82dd23e84be3 ("mm/vmalloc.c: preload a CPU with one object for split purpose") Reviewed-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>Acked-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Acked-by: Daniel Wagner <dwagner@xxxxxxx>
