lwn.git/kernel/trace/trace.c, branch docs-5.6

Fix up for "printk: Drop pr_warning definition"

2019-12-06T09:02:35+00:00

Link: http://lkml.kernel.org/r/20191206092503.303d6a57@canb.auug.org.au Cc: Linux Next Mailing List Cc: Linux Kernel Mailing List Cc: "Steven Rostedt (VMware)" Cc: Kefeng Wang Cc: Linus Torvalds Signed-off-by: Stephen Rothwell Signed-off-by: Petr Mladek

tracing: Do not create directories if lockdown is in affect

2019-12-04T13:27:15+00:00

If lockdown is disabling tracing on boot up, it prevents the tracing files from even bering created. But when that happens, there's several places that will give a warning that the files were not created as that is usually a sign of a bug. Add in strategic locations where a check is made to see if tracing is disabled by lockdown, and if it is, do not go further, and fail silently (but print that tracing is disabled by lockdown, without doing a WARN_ON()). Cc: Matthew Garrett Fixes: 17911ff38aa5 ("tracing: Add locked_down checks to the open calls of files created for tracefs") Signed-off-by: Steven Rostedt (VMware)

tracing: Adding new functions for kernel access to Ftrace instances

2019-11-23T00:41:08+00:00

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: use kvcalloc for tgid_map array allocation

2019-11-14T18:15:11+00:00

Fail to allocate memory for tgid_map, because it requires order-6 page. detail as: c3 sh: page allocation failure: order:6, mode:0x140c0c0(GFP_KERNEL), nodemask=(null) c3 sh cpuset=/ mems_allowed=0 c3 CPU: 3 PID: 5632 Comm: sh Tainted: G W O 4.14.133+ #10 c3 Hardware name: Generic DT based system c3 Backtrace: c3 [] (dump_backtrace) from [](show_stack+0x18/0x1c) c3 [] (show_stack) from [](dump_stack+0x84/0xa4) c3 [] (dump_stack) from [](warn_alloc+0xc4/0x19c) c3 [] (warn_alloc) from [](__alloc_pages_nodemask+0xd18/0xf28) c3 [] (__alloc_pages_nodemask) from [](kmalloc_order+0x20/0x38) c3 [] (kmalloc_order) from [](kmalloc_order_trace+0x24/0x108) c3 [] (kmalloc_order_trace) from [](set_tracer_flag+0xb0/0x158) c3 [] (set_tracer_flag) from [](trace_options_core_write+0x7c/0xcc) c3 [] (trace_options_core_write) from [](__vfs_write+0x40/0x14c) c3 [] (__vfs_write) from [](vfs_write+0xc4/0x198) c3 [] (vfs_write) from [](SyS_write+0x6c/0xd0) c3 [] (SyS_write) from [](ret_fast_syscall+0x0/0x54) Switch to use kvcalloc to avoid unexpected allocation failures. Link: http://lkml.kernel.org/r/1571888070-24425-1-git-send-email-chunyan.zhang@unisoc.com Signed-off-by: Yuming Han Signed-off-by: Chunyan Zhang Signed-off-by: Steven Rostedt (VMware)

tracing: Adding NULL checks for trace_array descriptor pointer

2019-11-13T14:37:29+00:00

As part of commit f45d1225adb0 ("tracing: Kernel access to Ftrace instances") we exported certain functions. Here, we are adding some additional NULL checks to ensure safe usage by users of these APIs. Link: http://lkml.kernel.org/r/1565805327-579-4-git-send-email-divya.indi@oracle.com Signed-off-by: Divya Indi Signed-off-by: Steven Rostedt (VMware)

tracing: Verify if trace array exists before destroying it.

2019-11-13T14:37:29+00:00

A trace array can be destroyed from userspace or kernel. Verify if the trace array exists before proceeding to destroy/remove it. Link: http://lkml.kernel.org/r/1565805327-579-3-git-send-email-divya.indi@oracle.com Reviewed-by: Aruna Ramakrishna Signed-off-by: Divya Indi [ Removed unneeded braces ] Signed-off-by: Steven Rostedt (VMware)

tracing: Use CONFIG_PREEMPTION

2019-11-13T14:37:28+00:00

CONFIG_PREEMPTION is selected by CONFIG_PREEMPT and by CONFIG_PREEMPT_RT. Both PREEMPT and PREEMPT_RT require the same functionality which today depends on CONFIG_PREEMPT. Add additional header output for PREEMPT_RT. Link: http://lkml.kernel.org/r/20191015191821.11479-34-bigeasy@linutronix.de Cc: Ingo Molnar Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt (VMware)

ftrace: Implement fs notification for tracing_max_latency

2019-11-13T14:37:28+00:00

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

2019-11-13T14:37:28+00:00

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: Initialize iter->seq after zeroing in tracing_read_pipe()

2019-10-13T00:49:34+00:00

A customer reported the following softlockup: [899688.160002] NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [test.sh:16464] [899688.160002] CPU: 0 PID: 16464 Comm: test.sh Not tainted 4.12.14-6.23-azure #1 SLE12-SP4 [899688.160002] RIP: 0010:up_write+0x1a/0x30 [899688.160002] Kernel panic - not syncing: softlockup: hung tasks [899688.160002] RIP: 0010:up_write+0x1a/0x30 [899688.160002] RSP: 0018:ffffa86784d4fde8 EFLAGS: 00000257 ORIG_RAX: ffffffffffffff12 [899688.160002] RAX: ffffffff970fea00 RBX: 0000000000000001 RCX: 0000000000000000 [899688.160002] RDX: ffffffff00000001 RSI: 0000000000000080 RDI: ffffffff970fea00 [899688.160002] RBP: ffffffffffffffff R08: ffffffffffffffff R09: 0000000000000000 [899688.160002] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8b59014720d8 [899688.160002] R13: ffff8b59014720c0 R14: ffff8b5901471090 R15: ffff8b5901470000 [899688.160002] tracing_read_pipe+0x336/0x3c0 [899688.160002] __vfs_read+0x26/0x140 [899688.160002] vfs_read+0x87/0x130 [899688.160002] SyS_read+0x42/0x90 [899688.160002] do_syscall_64+0x74/0x160 It caught the process in the middle of trace_access_unlock(). There is no loop. So, it must be looping in the caller tracing_read_pipe() via the "waitagain" label. Crashdump analyze uncovered that iter->seq was completely zeroed at this point, including iter->seq.seq.size. It means that print_trace_line() was never able to print anything and there was no forward progress. The culprit seems to be in the code: /* reset all but tr, trace, and overruns */ memset(&iter->seq, 0, sizeof(struct trace_iterator) - offsetof(struct trace_iterator, seq)); It was added by the commit 53d0aa773053ab182877 ("ftrace: add logic to record overruns"). It was v2.6.27-rc1. It was the time when iter->seq looked like: struct trace_seq { unsigned char buffer[PAGE_SIZE]; unsigned int len; }; There was no "size" variable and zeroing was perfectly fine. The solution is to reinitialize the structure after or without zeroing. Link: http://lkml.kernel.org/r/20191011142134.11997-1-pmladek@suse.com Signed-off-by: Petr Mladek Signed-off-by: Steven Rostedt (VMware)