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Re: [PATCH 2/3] Implement new features needed for handling SystemTap probes
- From: Tom Tromey <tromey at redhat dot com>
- To: Pedro Alves <palves at redhat dot com>
- Cc: Sergio Durigan Junior <sergiodj at redhat dot com>, gdb-patches at sourceware dot org
- Date: Thu, 15 Mar 2012 14:50:05 -0600
- Subject: Re: [PATCH 2/3] Implement new features needed for handling SystemTap probes
- References: <m3boo5cyd8.fsf@redhat.com> <m3pqclbjla.fsf@redhat.com> <4F620C71.8060501@redhat.com>
>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:
Pedro> I don't understand why we'd now skip the test when we don't have
Pedro> the unwinder stap probe,
I think the patch checks for the probe and for the unwinder debug hook,
and bails if they are both missing.
If either one exists then the test should work.
Pedro> This made me wonder about something else with this semaphore
Pedro> handling: the target can itself stop tracing, without GDB requesting
Pedro> it. E.g., if the trace buffer is full. If so, then you'll miss
Pedro> decrementing the semaphore count... Even worse with disconnected
Pedro> tracing; GDB might not even be connected when the tracing stops,
Pedro> and when you reconnect, you have no clue whether to decrement
Pedro> the counts or not...
Leaving the semaphore enabled in corner cases is not terrible.
It may affect performance a little, but that is all.
Anyone affected will already be doing reasonably sophisticated
debugging -- running disconnected trace experiments. If it is important
they could also just reset the semaphore to 0 manually.
Tom