Created attachment 184607 [details] malloc-user-process.d Here's how to repeat: 1. Install qTox and google perftools: pkg install qTox google-perftools 2. Load dtraceall kernel module: kldload dtraceall.ko 3. Place the attached scripts 'start-process-and-wait' and 'malloc-user-process.d' into some directory and set +x flag on both. 4. As a regular user, start qTox in stopped mode: LD_PRELOAD=/usr/local/lib/libtcmalloc.so ./start-process-and-wait /usr/local/bin/qtox 5. As root, with the pid printed on step 4, start dtrace: ./malloc-user-process.d {pid} > out.log In many cases, step 5 prints one of these two error messages and exits: > dtrace: failed to compile script ./malloc-user-process.d: line 9: Invalid argument or > dtrace: failed to compile script ./malloc-user-process.d: line 13: failed to create return probe for 'malloc': Unknown variable name In both cases the debugged process gets continued. In rare other cases dtrace continues and eventually deadlocks: > dtrace: script './malloc-user-process.d' matched 2 probes - at this point qtox process stays in TX+ state, and dtrace stays in S+ state forever. All errors are invalid. pidNNN argument should be valid in line 9, and malloc symbol is always present by the virtue of LD_PRELOAD of the library with 'malloc' symbol in it. dtrace shouldn't deadlock. Ctrl-C on dtrace doesn't stop it. However, 'killall -9 dtrace' does.
Created attachment 184608 [details] start-process-and-wait