On Wed, 2013-09-04 at 23:42 +0530, Hemant wrote: > On 09/04/2013 01:55 PM, Mark Wielaard wrote: > > Note that if you use the normal DTRACE_PROBE macros no semaphore will be > > inserted. And you can opt to not support probes that have a semaphore in > > perf if you think that is easier (just check the semaphore link-time > > address for the probe, it should normally be zero). Just warn: "No way I > > am going to probe something that might have a little extra overhead! I > > am no debugger..." :) > > I agree. There will be an extra overhead but there may be some important > markers (on which we need to probe) may be worth this overhead?
Yes, there maybe. And gdb and stap do support them. But it means not just setting the probe, but also incrementing (and decrementing) the semaphore. See "Semaphore Handling" under https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation Which is extra work, so for a minimal implementation that just supports normal (no-overhead) probes you might want to skip the extra work required to support them. I believe they are normally not used. I wouldn't recommend them and when I have added SDT probes myself I never used/needed them, but I haven't actually looked what others do. Cheers, Mark -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
