linux/kernel/trace/trace.h, branch v5.5

tracing: Introduce trace event injection

2019-12-02T16:07:00Z

We have been trying to use rasdaemon to monitor hardware errors like correctable memory errors. rasdaemon uses trace events to monitor various hardware errors. In order to test it, we have to inject some hardware errors, unfortunately not all of them provide error injections. MCE does provide a way to inject MCE errors, but errors like PCI error and devlink error don't, it is not easy to add error injection to each of them. Instead, it is relatively easier to just allow users to inject trace events in a generic way so that all trace events can be injected. This patch introduces trace event injection, where a new 'inject' is added to each tracepoint directory. Users could write into this file with key=value pairs to specify the value of each fields of the trace event, all unspecified fields are set to zero values by default. For example, for the net/net_dev_queue tracepoint, we can inject: INJECT=/sys/kernel/debug/tracing/events/net/net_dev_queue/inject echo "" > $INJECT echo "name='test'" > $INJECT echo "name='test' len=1024" > $INJECT cat /sys/kernel/debug/tracing/trace ... <...>-614 [000] .... 36.571483: net_dev_queue: dev= skbaddr=00000000fbf338c2 len=0 <...>-614 [001] .... 136.588252: net_dev_queue: dev=test skbaddr=00000000fbf338c2 len=0 <...>-614 [001] .N.. 208.431878: net_dev_queue: dev=test skbaddr=00000000fbf338c2 len=1024 Triggers could be triggered as usual too: echo "stacktrace if len == 1025" > /sys/kernel/debug/tracing/events/net/net_dev_queue/trigger echo "len=1025" > $INJECT cat /sys/kernel/debug/tracing/trace ... bash-614 [000] .... 36.571483: net_dev_queue: dev= skbaddr=00000000fbf338c2 len=0 bash-614 [001] .... 136.588252: net_dev_queue: dev=test skbaddr=00000000fbf338c2 len=0 bash-614 [001] .N.. 208.431878: net_dev_queue: dev=test skbaddr=00000000fbf338c2 len=1024 bash-614 [001] .N.1 284.236349: => event_inject_write => vfs_write => ksys_write => do_syscall_64 => entry_SYSCALL_64_after_hwframe The only thing that can't be injected is string pointers as they require constant string pointers, this can't be done at run time. Link: http://lkml.kernel.org/r/20191130045218.18979-1-xiyou.wangcong@gmail.com Cc: Ingo Molnar Signed-off-by: Cong Wang Signed-off-by: Steven Rostedt (VMware)

tracing: Adding new functions for kernel access to Ftrace instances

2019-11-23T00:41:08Z

Adding 2 new functions - 1) struct trace_array *trace_array_get_by_name(const char *name); Return pointer to a trace array with given name. If it does not exist, create and return pointer to the new trace array. 2) int trace_array_set_clr_event(struct trace_array *tr, const char *system ,const char *event, bool enable); Enable/Disable events to this trace array. Additionally, - To handle reference counters, export trace_array_put() - Due to introduction of the above 2 new functions, we no longer need to export - ftrace_set_clr_event & trace_array_create APIs. Link: http://lkml.kernel.org/r/1574276919-11119-2-git-send-email-divya.indi@oracle.com Signed-off-by: Divya Indi Reviewed-by: Aruna Ramakrishna Signed-off-by: Steven Rostedt (VMware)

tracing: Add missing "inline" in stub function of latency_fsnotify()

2019-11-15T03:45:47Z

The latency_fsnotify() stub when the function is not defined, was missing the "inline". Link: https://lore.kernel.org/r/20191115140213.74c5efe7@canb.auug.org.au Reported-by: Stephen Rothwell Signed-off-by: Steven Rostedt (VMware)

tracing: Declare newly exported APIs in include/linux/trace.h

2019-11-13T14:37:29Z

Declare the newly introduced and exported APIs in the header file - include/linux/trace.h. Moving previous declarations from kernel/trace/trace.h to include/linux/trace.h. Link: http://lkml.kernel.org/r/1565805327-579-2-git-send-email-divya.indi@oracle.com Signed-off-by: Divya Indi Signed-off-by: Steven Rostedt (VMware)

ftrace: Implement fs notification for tracing_max_latency

2019-11-13T14:37:28Z

This patch implements the feature that the tracing_max_latency file, e.g. /sys/kernel/debug/tracing/tracing_max_latency will receive notifications through the fsnotify framework when a new latency is available. One particularly interesting use of this facility is when enabling threshold tracing, through /sys/kernel/debug/tracing/tracing_thresh, together with the preempt/irqsoff tracers. This makes it possible to implement a user space program that can, with equal probability, obtain traces of latencies that occur immediately after each other in spite of the fact that the preempt/irqsoff tracers operate in overwrite mode. This facility works with the hwlat, preempt/irqsoff, and wakeup tracers. The tracers may call the latency_fsnotify() from places such as __schedule() or do_idle(); this makes it impossible to call queue_work() directly without risking a deadlock. The same would happen with a softirq, kernel thread or tasklet. For this reason we use the irq_work mechanism to call queue_work(). This patch creates a new workqueue. The reason for doing this is that I wanted to use the WQ_UNBOUND and WQ_HIGHPRI flags. My thinking was that WQ_UNBOUND might help with the latency in some important cases. If we use: queue_work(system_highpri_wq, &tr->fsnotify_work); then the work will (almost) always execute on the same CPU but if we are unlucky that CPU could be too busy while there could be another CPU in the system that would be able to process the work soon enough. queue_work_on() could be used to queue the work on another CPU but it seems difficult to select the right CPU. Link: http://lkml.kernel.org/r/20191008220824.7911-2-viktor.rosendahl@gmail.com Reviewed-by: Joel Fernandes (Google) Signed-off-by: Viktor Rosendahl (BMW) [ Added max() to have one compare for max latency ] Signed-off-by: Steven Rostedt (VMware)

ftrace: Add information on number of page groups allocated

2019-11-13T14:37:28Z

Looking for ways to shrink the size of the dyn_ftrace structure, knowing the information about how many pages and the number of groups of those pages, is useful in working out the best ways to save on memory. This adds one info print on how many groups of pages were used to allocate the ftrace dyn_ftrace structures, and also shows the number of pages and groups in the dyn_ftrace_total_info (which is used for debugging). Signed-off-by: Steven Rostedt (VMware)

tracing: Add tracing_check_open_get_tr()

2019-10-13T00:44:07Z

Currently, most files in the tracefs directory test if tracing_disabled is set. If so, it should return -ENODEV. The tracing_disabled is called when tracing is found to be broken. Originally it was done in case the ring buffer was found to be corrupted, and we wanted to prevent reading it from crashing the kernel. But it's also called if a tracing selftest fails on boot. It's a one way switch. That is, once it is triggered, tracing is disabled until reboot. As most tracefs files can also be used by instances in the tracefs directory, they need to be carefully done. Each instance has a trace_array associated to it, and when the instance is removed, the trace_array is freed. But if an instance is opened with a reference to the trace_array, then it requires looking up the trace_array to get its ref counter (as there could be a race with it being deleted and the open itself). Once it is found, a reference is added to prevent the instance from being removed (and the trace_array associated with it freed). Combine the two checks (tracing_disabled and trace_array_get()) into a single helper function. This will also make it easier to add lockdown to tracefs later. Link: http://lkml.kernel.org/r/20191011135458.7399da44@gandalf.local.home Signed-off-by: Steven Rostedt (VMware)

tracing: Have trace events system open call tracing_open_generic_tr()

2019-10-13T00:43:00Z

Instead of having the trace events system open call open code the taking of the trace_array descriptor (with trace_array_get()) and then calling trace_open_generic(), have it use the tracing_open_generic_tr() that does the combination of the two. This requires making tracing_open_generic_tr() global. Signed-off-by: Steven Rostedt (VMware)

tracing: Fix clang -Wint-in-bool-context warnings in IF_ASSIGN macro

2019-09-28T21:13:39Z

After r372664 in clang, the IF_ASSIGN macro causes a couple hundred warnings along the lines of: kernel/trace/trace_output.c:1331:2: warning: converting the enum constant to a boolean [-Wint-in-bool-context] kernel/trace/trace.h:409:3: note: expanded from macro 'trace_assign_type' IF_ASSIGN(var, ent, struct ftrace_graph_ret_entry, ^ kernel/trace/trace.h:371:14: note: expanded from macro 'IF_ASSIGN' WARN_ON(id && (entry)->type != id); \ ^ 264 warnings generated. This warning can catch issues with constructs like: if (state == A || B) where the developer really meant: if (state == A || state == B) This is currently the only occurrence of the warning in the kernel tree across defconfig, allyesconfig, allmodconfig for arm32, arm64, and x86_64. Add the implicit '!= 0' to the WARN_ON statement to fix the warnings and find potential issues in the future. Link: https://github.com/llvm/llvm-project/commit/28b38c277a2941e9e891b2db30652cfd962f070b Link: https://github.com/ClangBuiltLinux/linux/issues/686 Link: http://lkml.kernel.org/r/20190926162258.466321-1-natechancellor@gmail.com Reviewed-by: Nick Desaulniers Signed-off-by: Nathan Chancellor Signed-off-by: Steven Rostedt (VMware)

tracing: Rename tracing_reset() to tracing_reset_cpu()

2019-08-31T16:19:40Z

The name tracing_reset() was a misnomer, as it really only reset a single CPU buffer. Rename it to tracing_reset_cpu() and also make it static and remove the prototype from trace.h, as it is only used in a single function. Signed-off-by: Steven Rostedt (VMware)