Re: [PATCH] ptrace: add ability to retrieve signals withoutremoving them from a queue

From: Oleg Nesterov
Date: Wed Feb 13 2013 - 11:08:12 EST

On 02/13, Andrey Vagin 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.
> All other bits of addr is used for flags. Currently here is only one
> flag PTRACE_PEEK_SHARED for dumping signals from process-wide shared
> queue. If this flag is not set, a signal is read from a per-thread
> queue. A result siginfo contains a kernel part of si_code which usually
> striped, but it's required for queuing the same siginfo back during
> restore of pending signals.
> If a signal with the specified sequence number doesn't exist, ptrace
> returns ENOENT.
> This functionality is required for checkpointing pending signals.

I thinks the patch is correct, and personally I like very much the fact
it is simple. Compared to misc signalfd hacks we discussed before.


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