[Bug translator/10995] on-the-fly enabled/disabled probes

[jlebon at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=10995

Jonathan Lebon <jlebon at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jlebon at redhat dot com

--- Comment #3 from Jonathan Lebon <jlebon at redhat dot com> ---
I've been working on this feature for a while. I've just pushed to the
jlebon/onthefly branch preliminary work to support this. Currently supported
are hrtimer probes and kprobes.

You can use the -DDEBUG_STP_ON_THE_FLY directive to see it in action during
runtime (outputs to dmesg). Here's a sample (with relevant dmesg output
interspersed):

$ stap -DDEBUG_STP_ON_THE_FLY -e '
global enabled = 0
probe timer.s(1) if (enabled) {
   println("enabled!")
}
probe timer.s(5) {
   println("toggling enable")
   enabled = !enabled
}'



***** DMESG *****
[ 1490.643619] stap_9ea625b9fc91177d0b2a6490acd27b5_20639: systemtap:
2.6/0.158, base: ffffffffa0295000, memory: 31data/24text/1ctx/2058net/17alloc
kb, probes: 2
[ 1490.643625] systemtap_module_init:470 not starting (hrtimer) pidx 0
[ 1490.644421] systemtap_module_init:486 started (hrtimer) pidx 1
*****************



toggling enable



***** DMESG *****
[ 1495.644483] _stp_hrtimer_notify_function:298 scheduling work
[ 1495.645261] module_refresher:68 calling systemtap_module_refresh()
[ 1495.645474] systemtap_module_refresh:538 enabling (hrtimer) pidx 0
*****************



enabled!
enabled!
enabled!
enabled!
toggling enable



***** DMESG *****
[ 1500.644483] _stp_hrtimer_notify_function:298 scheduling work
[ 1500.645275] module_refresher:68 calling systemtap_module_refresh()
[ 1500.646036] systemtap_module_refresh:541 disabling (hrtimer) pidx 0
*****************



toggling enable



***** DMESG *****
[ 1505.644484] _stp_hrtimer_notify_function:298 scheduling work
[ 1505.645287] module_refresher:68 calling systemtap_module_refresh()
[ 1505.646069] systemtap_module_refresh:538 enabling (hrtimer) pidx 0
*****************

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