From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965276AbaLMFul (ORCPT ); Sat, 13 Dec 2014 00:50:41 -0500 Received: from smtprelay0184.hostedemail.com ([216.40.44.184]:33504 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965236AbaLMFuk (ORCPT ); Sat, 13 Dec 2014 00:50:40 -0500 X-Session-Marker: 6E657665747340676F6F646D69732E6F7267 X-Spam-Summary: 50,0,0,,d41d8cd98f00b204,rostedt@goodmis.org,:::::::::::::::::::::::::,RULES_HIT:2:41:355:379:541:800:960:967:973:988:989:1260:1277:1311:1313:1314:1345:1359:1437:1515:1516:1518:1535:1593:1594:1605:1730:1747:1777:1792:1801:2393:2525:2560:2563:2682:2685:2693:2859:2902:2933:2937:2939:2942:2945:2947:2951:2954:3022:3138:3139:3140:3141:3142:3865:3867:3868:3871:3872:3874:3934:3936:3938:3941:3944:3947:3950:3953:3956:3959:4049:4118:4321:4605:5007:6119:6120:6261:6742:8599:9025:10004:10848:11026:11232:11473:11658:11914:12043:12291:12296:12438:12517:12519:12555:12679:12683:12783:13161:13180:13229:14096:14097:21080,0,RBL:none,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fn,MSBL:0,DNSBL:none,Custom_rules:0:0:0 X-HE-Tag: top42_79ef74ce5155f X-Filterd-Recvd-Size: 7572 Date: Sat, 13 Dec 2014 00:50:37 -0500 From: Steven Rostedt To: Thomas Gleixner Cc: LKML , Jiang Liu , x86@kernel.org, Linus Torvalds , Andrew Morton , Bjorn Helgaas , Tony Luck , Borislav Petkov , Joerg Roedel , Marc Zyngier , Yinghai Lu , Alex Williamson Subject: [RFC PATCH 2/2] tracing: Add tracepoint_printk cmdline Message-ID: <20141213005037.78eca245@gandalf.local.home> In-Reply-To: <20141213004830.792da019@gandalf.local.home> References: <20141212181420.47100d5c@gandalf.local.home> <20141213004830.792da019@gandalf.local.home> X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.25; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add the kernel command line tracepoint_printk option that will have tracepoints that are active sent to printk(). Passing "tracepoint_printk" will activate this. To turn it off the sysctl /proc/sys/kernel/tracepoint_printk can have '0' echoed into it. Note, this only works if the cmdline option is used. Echoing 1 into the sysctl file without the cmdline option will have no affect. Note, this is a dangerous option. Having high frequency tracepoints send their data to printk() can possibly cause a live lock. Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1412121539300.16494@nanos Suggested-by: Thomas Gleixner Signed-off-by: Steven Rostedt --- Documentation/kernel-parameters.txt | 18 ++++++++++++++++++ include/linux/ftrace.h | 1 + kernel/sysctl.c | 7 +++++++ kernel/trace/trace.c | 17 +++++++++++++++++ kernel/trace/trace.h | 1 + kernel/trace/trace_events.c | 32 ++++++++++++++++++++++++++++++++ 6 files changed, 76 insertions(+) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 1d09eb37c562..d81f464a7358 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -3500,6 +3500,24 @@ bytes respectively. Such letter suffixes can also be entirely omitted. See also Documentation/trace/ftrace.txt "trace options" section. + tracepoint_printk[FTRACE] + Have the tracepoints sent to printk as well as the + tracing ring buffer. This is useful for early boot up + where the system hangs or reboots and does not give the + option for reading the tracing buffer or performing a + ftrace_dump_on_oops. + + To turn off having tracepoints sent to printk, + echo 0 > /proc/sys/kernel/tracepoint_printk + Note, echoing 1 into this file without the + tracepoint_printk kernel cmdline option has no effect. + + ** CAUTION ** + + Having tracepoints sent to printk() and activating high + frequency tracepoints such as irq or sched, can cause + the system to live lock. + traceoff_on_warning [FTRACE] enable this option to disable tracing when a warning is hit. This turns off "tracing_on". Tracing can diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 0fc3e720d4fd..9e20e7c28aab 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -879,6 +879,7 @@ static inline int test_tsk_trace_graph(struct task_struct *tsk) enum ftrace_dump_mode; extern enum ftrace_dump_mode ftrace_dump_on_oops; +extern int tracepoint_printk; extern void disable_trace_on_warning(void); extern int __disable_trace_on_warning; diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 4aada6d9fe74..bb50c2187194 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -622,6 +622,13 @@ static struct ctl_table kern_table[] = { .mode = 0644, .proc_handler = proc_dointvec, }, + { + .procname = "tracepoint_printk", + .data = &tracepoint_printk, + .maxlen = sizeof(tracepoint_printk), + .mode = 0644, + .proc_handler = proc_dointvec, + }, #endif #ifdef CONFIG_KEXEC { diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index ec3ca694665f..18a00ab4427e 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -63,6 +63,10 @@ static bool __read_mostly tracing_selftest_running; */ bool __read_mostly tracing_selftest_disabled; +/* Pipe tracepoints to printk */ +struct trace_iterator *tracepoint_print_iter; +int tracepoint_printk; + /* For tracers that don't implement custom flags */ static struct tracer_opt dummy_tracer_opt[] = { { } @@ -193,6 +197,13 @@ static int __init set_trace_boot_clock(char *str) } __setup("trace_clock=", set_trace_boot_clock); +static int __init set_tracepoint_printk(char *str) +{ + if ((strcmp(str, "=0") != 0 && strcmp(str, "=off") != 0)) + tracepoint_printk = 1; + return 1; +} +__setup("tracepoint_printk", set_tracepoint_printk); unsigned long long ns2usecs(cycle_t nsec) { @@ -6878,6 +6889,12 @@ out: void __init trace_init(void) { + if (tracepoint_printk) { + tracepoint_print_iter = + kmalloc(sizeof(*tracepoint_print_iter), GFP_KERNEL); + if (WARN_ON(!tracepoint_print_iter)) + tracepoint_printk = 0; + } tracer_alloc_buffers(); init_ftrace_syscalls(); trace_event_init(); diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index c138c149d6ef..8de48bac1ce2 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1313,5 +1313,6 @@ void trace_event_init(void); static inline void __init trace_event_init(void) { } #endif +extern struct trace_iterator *tracepoint_print_iter; #endif /* _LINUX_KERNEL_TRACE_H */ diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index fd9deb0e03f0..9f7175a3df71 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -212,8 +212,40 @@ void *ftrace_event_buffer_reserve(struct ftrace_event_buffer *fbuffer, } EXPORT_SYMBOL_GPL(ftrace_event_buffer_reserve); +static DEFINE_SPINLOCK(tracepoint_iter_lock); + +static void output_printk(struct ftrace_event_buffer *fbuffer) +{ + struct ftrace_event_call *event_call; + struct trace_event *event; + unsigned long flags; + struct trace_iterator *iter = tracepoint_print_iter; + + if (!iter) + return; + + event_call = fbuffer->ftrace_file->event_call; + if (!event_call || !event_call->event.funcs || + !event_call->event.funcs->trace) + return; + + event = &fbuffer->ftrace_file->event_call->event; + + spin_lock_irqsave(&tracepoint_iter_lock, flags); + trace_seq_init(&iter->seq); + iter->ent = fbuffer->entry; + event_call->event.funcs->trace(iter, 0, event); + trace_seq_putc(&iter->seq, 0); + printk("%s", iter->seq.buffer); + + spin_unlock_irqrestore(&tracepoint_iter_lock, flags); +} + void ftrace_event_buffer_commit(struct ftrace_event_buffer *fbuffer) { + if (tracepoint_printk) + output_printk(fbuffer); + event_trigger_unlock_commit(fbuffer->ftrace_file, fbuffer->buffer, fbuffer->event, fbuffer->entry, fbuffer->flags, fbuffer->pc); -- 1.8.1.4