Messages in this thread |  | | Date | Sun, 29 Oct 2000 02:16:42 +0100 | From | Andi Kleen <> | Subject | Re: tcp_do_sendmsg() allocation still broken ? |
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On Sat, Oct 28, 2000 at 09:13:27PM -0200, Marcelo Tosatti wrote: > > > On Sun, 29 Oct 2000, Andi Kleen wrote: > > > On Sat, Oct 28, 2000 at 07:12:44PM -0200, Marcelo Tosatti wrote: > > > > > > David, > > > > > > tcp_do_sendmsg() still allocates using GFP_KERNEL when it can't, it seems: > > > > tcp_do_sendmsg() should only be called from process context, because it can > > sleep for other reasons anyways. > > > > If someone calls it from interrupt context it needs to be fixed. > > Andi, > > Think about nbd.
Making tcp_do_sendmsg use GFP_ATOMIC would make it too unreliable for other situations. Penalizing the whole system just for nbd is not a good idea.
> > It allocates memory inside its request function, and since we do write > throttling in try_to_free_pages() we can end up with this deadlock in low > memory conditions: > > nbd_do_request -> nbd_send_req -> nbd_xmit -> sock_sendmsg -> ... -> > tcp_do_sendmsg -> tcp_send_skb -> skb_copy -> alloc_skb -> > kmalloc(GFP_KERNEL) -> kmem_cache_grow -> get_free_pages -> > try_to_free_pages -> shrink_mmap -> try_to_free_buffers -> > sync_page_buffers -> ll_rw_block -> make_request -> add_request -> > nbd_do_request -> nbd_send_req -> ... > > until there are no more free requests on the request queue and writer > processes stuck on __get_request_wait.
Looks like a job for PF_MEMALLOC and making GFP_KERNEL fail earlier.
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