Messages in this thread | | | Date | Thu, 10 May 2001 23:13:00 +0200 | From | Andrea Arcangeli <> | Subject | Re: Deadlock in 2.2 sock_alloc_send_skb? |
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On Thu, May 10, 2001 at 07:30:47PM +0200, Andi Kleen wrote: > On Thu, May 10, 2001 at 01:57:49PM +0100, Alan Cox wrote: > > > If that happens, and the socket uses GFP_ATOMIC allocation, the while (1) > > > loop in sock_alloc_send_skb() will endlessly spin, without ever calling > > > schedule(), and all the time holding the kernel lock ... > > > > If the socket is using GFP_ATOMIC allocation it should never loop. That is > > -not-allowed-. > > It is just not clear why any socket should use GFP_ATOMIC. I can understand > it using GFP_BUFFER e.g. for nbd, but GFP_ATOMIC seems to be rather radical > and fragile.
side note, the only legal use of GFP_ATOMIC in sock_alloc_send_skb is with noblock set and fallback zero, remeber GFP_BUFFER will sleep, it may not sleep in vanilla 2.2.19 but the necessary lowlatency hooks in the memory balancing that for example I have on my 2.2 tree will make it to sleep.
The patch self contained looks perfect (I didn't checked that the callers are happy with a -ENOMEM errorcode though), if alloc_skb() failed that's a plain -ENOMEM. The caller must _not_ try again, they must take a recovery fail path instead.
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