Messages in this thread | | | Date | Wed, 20 Feb 2013 23:37:03 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH] ptrace: add ability to retrieve signals without removing them from a queue |
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On 02/19, Pavel Emelyanov wrote: > > On 02/19/2013 11:34 PM, Oleg Nesterov wrote: > > But, given that every PEEK does list_for_each() until it finds the > > necessary sequence number, I am wondering how this O(n**2) will work > > if you want to dump 126065 signals ;) > > Isn't it the great reason for making the addr point to a structure, that > would look like > > struct siginfo_peek_arg { > unsigned flags; /* all bits but 0th, that selects between private/shared > queues, should be zero */ > unsigned int off; /* from which siginfo to start */ > unsigned int nr; /* how may siginfos to take */ > };
I am fine either way, to me everything looks better than signalfd hacks.
But if you meant "avoid n^2", this won't help? You can't do copy_siginfo_to_user() under ->siglock, so you need to restart list_for_each() anyway.
Oleg.
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