From mboxrd@z Thu Jan 1 00:00:00 1970 From: saiprakash.ranjan@codeaurora.org (Sai Prakash Ranjan) Date: Wed, 26 Sep 2018 15:16:05 +0530 Subject: [PATCH 3/6] tracing: Add tp_pstore cmdline to have tracepoints go to pstore In-Reply-To: References: Message-ID: <1f546234-bd7b-448a-3666-3f8baa249608@codeaurora.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 9/26/2018 2:55 AM, Joel Fernandes wrote: > On Sat, Sep 8, 2018 at 1:28 PM Sai Prakash Ranjan > wrote: >> >> Add the kernel command line tp_pstore option that will have >> tracepoints go to persistent ram buffer as well as to the >> trace buffer for further debugging. This is similar to tp_printk >> cmdline option of ftrace. >> >> Pstore support for event tracing is already added and we enable >> logging to pstore only if cmdline is specified. >> >> Passing "tp_pstore" will activate logging to pstore. To turn it >> off, the sysctl /proc/sys/kernel/tracepoint_pstore 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. >> >> Signed-off-by: Sai Prakash Ranjan >> --- >> .../admin-guide/kernel-parameters.txt | 21 ++++++++ >> include/linux/ftrace.h | 6 ++- >> kernel/sysctl.c | 7 +++ >> kernel/trace/Kconfig | 22 +++++++- >> kernel/trace/trace.c | 51 +++++++++++++++++++ >> kernel/trace/trace.h | 7 +++ >> 6 files changed, 112 insertions(+), 2 deletions(-) >> > [...] >> config GCOV_PROFILE_FTRACE >> bool "Enable GCOV profiling on ftrace subsystem" >> depends on GCOV_KERNEL >> @@ -789,4 +810,3 @@ config GCOV_PROFILE_FTRACE >> endif # FTRACE >> >> endif # TRACING_SUPPORT >> - >> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c >> index bf6f1d70484d..018cbbefb769 100644 >> --- a/kernel/trace/trace.c >> +++ b/kernel/trace/trace.c >> @@ -73,6 +73,11 @@ struct trace_iterator *tracepoint_print_iter; >> int tracepoint_printk; >> static DEFINE_STATIC_KEY_FALSE(tracepoint_printk_key); >> >> +/* Pipe tracepoints to pstore */ >> +struct trace_iterator *tracepoint_pstore_iter; >> +int tracepoint_pstore; >> +static DEFINE_STATIC_KEY_FALSE(tracepoint_pstore_key); >> + >> /* For tracers that don't implement custom flags */ >> static struct tracer_opt dummy_tracer_opt[] = { >> { } >> @@ -238,6 +243,14 @@ static int __init set_tracepoint_printk(char *str) >> } >> __setup("tp_printk", set_tracepoint_printk); >> >> +static int __init set_tracepoint_pstore(char *str) >> +{ >> + if ((strcmp(str, "=0") != 0 && strcmp(str, "=off") != 0)) >> + tracepoint_pstore = 1; >> + return 1; >> +} >> +__setup("tp_pstore", set_tracepoint_pstore); >> + >> unsigned long long ns2usecs(u64 nsec) >> { >> nsec += 500; >> @@ -2376,11 +2389,45 @@ int tracepoint_printk_sysctl(struct ctl_table *table, int write, >> return ret; >> } >> >> +static DEFINE_MUTEX(tracepoint_pstore_mutex); >> + >> +int tracepoint_pstore_sysctl(struct ctl_table *table, int write, >> + void __user *buffer, size_t *lenp, >> + loff_t *ppos) >> +{ >> + int save_tracepoint_pstore; >> + int ret; >> + >> + mutex_lock(&tracepoint_pstore_mutex); >> + save_tracepoint_pstore = tracepoint_pstore; >> + >> + ret = proc_dointvec(table, write, buffer, lenp, ppos); >> + >> + if (!tracepoint_pstore_iter) >> + tracepoint_pstore = 0; >> + >> + if (save_tracepoint_pstore == tracepoint_pstore) >> + goto out; >> + >> + if (tracepoint_pstore) >> + static_key_enable(&tracepoint_pstore_key.key); >> + else >> + static_key_disable(&tracepoint_pstore_key.key); >> + >> + out: >> + mutex_unlock(&tracepoint_pstore_mutex); >> + >> + return ret; >> +} >> + >> void trace_event_buffer_commit(struct trace_event_buffer *fbuffer) >> { >> if (static_key_false(&tracepoint_printk_key.key)) >> output_printk(fbuffer); >> >> + if (static_key_false(&tracepoint_pstore_key.key)) >> + pstore_event_call(fbuffer); > > Can you not find a way to pass the size of the even record here, to > pstore? Then you can directly allocate and store the binary record in > pstore itself instead of rendering and storing the text in pstore > which will be more space (and I think time) efficient. I also think if > you do this, then you will not need to use the spinlock in the pstore > (which AIUI is preventing the warning you're seeing in the > event_call->event.funcs->trace() call). > Right, I can check this out. Thanks, Sai -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation