Messages in this thread | | | Date | Tue, 19 Feb 2013 20:34:24 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH] ptrace: add ability to retrieve signals without removing them from a queue |
| |
On 02/19, Pavel Emelyanov wrote: > > On 02/19/2013 04:15 PM, Michael Kerrisk (man-pages) wrote: > > On Wed, Feb 13, 2013 at 4:16 PM, Andrey Vagin <avagin@openvz.org> wrote: > >> This patch adds a new ptrace request PTRACE_PEEKSIGINFO. > >> > >> This request is used to retrieve information about a signal with the > >> specified sequence number. A siginfo_t structure is copied from the child > >> to location data in the parent. > >> > >> The low 16 bits of addr contains a sequence number of signal in a queue: > > > > I think 16 bits is probably not enough.... Already, on the "out of the > > box" system that I have at hand, one can queue more than 2^16-1 > > signals: > > > > $ cat /proc/$$/status | grep SigQ > > SigQ: 2/126065 > > Yup :( Well, actually it would be enough to have only 1 bit as "flags" > and the rest (31 at least) for the number. But taking into account > Oleg's wish to have an ability to extend the amount of flags
I am not sure this is really needed, and we can add more PTRACE_PEEK_ codes later. I am fine either way, we can even add PEEK_PRIVATE/SHARED right now.
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 ;)
Oleg.
| |