mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-15 01:36:46 +07:00
f217c44ebd
my slides for the event trigger tutorial. I booted a 3.14-rc7 kernel to perform what I wanted to teach and cut and paste it into my slides. When I tried the traceon event trigger with a condition attached to it (turns tracing on only if a field of the trigger event matches a condition set by the user), nothing happened. Tracing would not turn on. I stopped working on my presentation in order to find what was wrong. It ended up being the way trace event triggers work when they have conditions. Instead of copying the fields, the condition code just looks at the fields that were copied into the ring buffer. This works great, unless tracing is off. That's because when the event is reserved on the ring buffer, the ring buffer returns a NULL pointer, this tells the tracing code that the ring buffer is disabled. This ends up being a problem for the traceon trigger if it is using this information to check its condition. Luckily the code that checks if tracing is on returns the ring buffer to use (because the ring buffer is determined by the event file also passed to that field). I was able to easily solve this bug by checking in that helper function if the returned ring buffer entry is NULL, and if so, also check the file flag if it has a trace event trigger condition, and if so, to pass back a temp ring buffer to use. This will allow the trace event trigger condition to still test the event fields, but nothing will be recorded. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAABAgAGBQJTMtD2AAoJEKQekfcNnQGuwrUH/juk/qKY7T/nq98iMleOD+LR iTQyWh9zvHdku/3ZlK5eJqla2TJUctM5Sf9WhvV/iXJ2/9m5qnekZ6gCoraGVpG4 qfKZAiHdGU0sFdp2NIt1uIHcqjYc8dg2KGajEKGNr7E2F3fvSTfNZV+WKAnmGqlE 8ICsoYJ/Uv4kh18QQJexbyd7jXWE8tzxxS9UzPvCtCiSd1xf2yCAS5OlwPYafgiv Egbjqq7IUCJfVb0h/YfgPbEW69sjlxOulzn42Nii+UOx9uv1RTdtXdivyCXDWfX3 Que0Do757oTvpW/22s9T3mpUtYLCB+6B2GV+ljqbLCZ5pRywc/GDCU//D1AXKEI= =dKWH -----END PGP SIGNATURE----- Merge tag 'trace-fixes-v3.14-rc7-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace Pull tracing fix from Steven Rostedt: "While on my flight to Linux Collaboration Summit, I was working on my slides for the event trigger tutorial. I booted a 3.14-rc7 kernel to perform what I wanted to teach and cut and paste it into my slides. When I tried the traceon event trigger with a condition attached to it (turns tracing on only if a field of the trigger event matches a condition set by the user), nothing happened. Tracing would not turn on. I stopped working on my presentation in order to find what was wrong. It ended up being the way trace event triggers work when they have conditions. Instead of copying the fields, the condition code just looks at the fields that were copied into the ring buffer. This works great, unless tracing is off. That's because when the event is reserved on the ring buffer, the ring buffer returns a NULL pointer, this tells the tracing code that the ring buffer is disabled. This ends up being a problem for the traceon trigger if it is using this information to check its condition. Luckily the code that checks if tracing is on returns the ring buffer to use (because the ring buffer is determined by the event file also passed to that field). I was able to easily solve this bug by checking in that helper function if the returned ring buffer entry is NULL, and if so, also check the file flag if it has a trace event trigger condition, and if so, to pass back a temp ring buffer to use. This will allow the trace event trigger condition to still test the event fields, but nothing will be recorded" * tag 'trace-fixes-v3.14-rc7-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing: Fix traceon trigger condition to actually turn tracing on |
||
|---|---|---|
| .. | ||
| cpu | ||
| debug | ||
| events | ||
| gcov | ||
| irq | ||
| locking | ||
| power | ||
| printk | ||
| rcu | ||
| sched | ||
| time | ||
| trace | ||
| .gitignore | ||
| acct.c | ||
| async.c | ||
| audit_tree.c | ||
| audit_watch.c | ||
| audit.c | ||
| audit.h | ||
| auditfilter.c | ||
| auditsc.c | ||
| backtracetest.c | ||
| bounds.c | ||
| capability.c | ||
| cgroup_freezer.c | ||
| cgroup.c | ||
| compat.c | ||
| configs.c | ||
| context_tracking.c | ||
| cpu_pm.c | ||
| cpu.c | ||
| cpuset.c | ||
| crash_dump.c | ||
| cred.c | ||
| delayacct.c | ||
| dma.c | ||
| elfcore.c | ||
| exec_domain.c | ||
| exit.c | ||
| extable.c | ||
| fork.c | ||
| freezer.c | ||
| futex_compat.c | ||
| futex.c | ||
| groups.c | ||
| hrtimer.c | ||
| hung_task.c | ||
| irq_work.c | ||
| itimer.c | ||
| jump_label.c | ||
| kallsyms.c | ||
| kcmp.c | ||
| Kconfig.freezer | ||
| Kconfig.hz | ||
| Kconfig.locks | ||
| Kconfig.preempt | ||
| kexec.c | ||
| kmod.c | ||
| kprobes.c | ||
| ksysfs.c | ||
| kthread.c | ||
| latencytop.c | ||
| Makefile | ||
| module_signing.c | ||
| module-internal.h | ||
| module.c | ||
| notifier.c | ||
| nsproxy.c | ||
| padata.c | ||
| panic.c | ||
| params.c | ||
| pid_namespace.c | ||
| pid.c | ||
| posix-cpu-timers.c | ||
| posix-timers.c | ||
| profile.c | ||
| ptrace.c | ||
| range.c | ||
| reboot.c | ||
| relay.c | ||
| res_counter.c | ||
| resource.c | ||
| seccomp.c | ||
| signal.c | ||
| smp.c | ||
| smpboot.c | ||
| smpboot.h | ||
| softirq.c | ||
| stacktrace.c | ||
| stop_machine.c | ||
| sys_ni.c | ||
| sys.c | ||
| sysctl_binary.c | ||
| sysctl.c | ||
| system_certificates.S | ||
| system_keyring.c | ||
| task_work.c | ||
| taskstats.c | ||
| test_kprobes.c | ||
| time.c | ||
| timeconst.bc | ||
| timer.c | ||
| tracepoint.c | ||
| tsacct.c | ||
| uid16.c | ||
| up.c | ||
| user_namespace.c | ||
| user-return-notifier.c | ||
| user.c | ||
| utsname_sysctl.c | ||
| utsname.c | ||
| watchdog.c | ||
| workqueue_internal.h | ||
| workqueue.c | ||