Yang Shi wrote: > On 9/27/17 9:36 PM, Tetsuo Handa wrote: > > On 2017/09/28 6:46, Yang Shi wrote: > >> Changelog v7 -> v8: > >> * Adopted Michal’s suggestion to dump unreclaim slab info when > >> unreclaimable slabs amount > total user memory. Not only in oom panic path. > > > > Holding slab_mutex inside dump_unreclaimable_slab() was refrained since V2 > > because there are > > > > mutex_lock(&slab_mutex); > > kmalloc(GFP_KERNEL); > > mutex_unlock(&slab_mutex); > > > > users. If we call dump_unreclaimable_slab() for non OOM panic path, aren't > > we > > introducing a risk of crash (i.e. kernel panic) for regular OOM path? > > I don't see the difference between regular oom path and oom path other > than calling panic() at last. > > And, the slab dump may be called by panic path too, it is for both > regular and panic path.
Calling a function that might cause kerneloops immediately before calling panic() would be tolerable, for the kernel will panic after all. But calling a function that might cause kerneloops when there is no plan to call panic() is a bug. > > Thanks, > Yang > > > > > We can try mutex_trylock() from dump_unreclaimable_slab() at best. > > But it is still remaining unsafe, isn't it? > > >
