On Mon, Oct 24, 2011 at 7:19 AM, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote: > > Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx> writes: > > > We need a cpumask to track cpus with per cpu cache pages > > to know which cpu to whack during flush_all. For > > CONFIG_CPUMASK_OFFSTACK=n we allocate the mask on stack. > > For CONFIG_CPUMASK_OFFSTACK=y we don't want to call kmalloc > > on the flush_all path, so we preallocate per kmem_cache > > on cache creation and use it in flush_all. > > What's the problem with calling kmalloc in flush_all? > That's a slow path anyways, isn't it? > > I believe the IPI functions usually allocate anyways. > > So maybe you can do that much simpler. That was what the first version of the patch did (use alloc_cpumask_var in flush_all). Pekka Enberg pointed out that calling kmalloc on the kmem_cache shrinking code path is not a good idea and it does sound like a deadlock waiting to happen. Gilad -- Gilad Ben-Yossef Chief Coffee Drinker gilad@xxxxxxxxxxxxx Israel Cell: +972-52-8260388 US Cell: +1-973-8260388 http://benyossef.com "I've seen things you people wouldn't believe. Goto statements used to implement co-routines. I watched C structures being stored in registers. All those moments will be lost in time... like tears in rain... Time to die. " -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>