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Date: Wed, 18 Jul 2012 09:10:21 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Anton Vorontsov <anton.vorontsov@...aro.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Kees Cook <keescook@...omium.org>,
Colin Cross <ccross@...roid.com>,
Tony Luck <tony.luck@...el.com>,
Frederic Weisbecker <fweisbec@...il.com>,
Ingo Molnar <mingo@...hat.com>, Arnd Bergmann <arnd@...db.de>,
John Stultz <john.stultz@...aro.org>,
Shuah Khan <shuahkhan@...il.com>, arve@...roid.com,
Rebecca Schultz Zavin <rebecca@...roid.com>,
Jesper Juhl <jj@...osbits.net>,
Randy Dunlap <rdunlap@...otime.net>,
Stephen Boyd <sboyd@...eaurora.org>,
Thomas Meyer <thomas@...3r.de>,
Andrew Morton <akpm@...ux-foundation.org>,
Marco Stornelli <marco.stornelli@...il.com>,
WANG Cong <xiyou.wangcong@...il.com>,
linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org,
linaro-kernel@...ts.linaro.org, patches@...aro.org,
kernel-team@...roid.com
Subject: Re: [PATCH] pstore/ftrace: Convert to its own enable/disable
debugfs knob
On Tue, 2012-07-17 at 20:47 -0700, Anton Vorontsov wrote:
> diff --git a/Documentation/ramoops.txt b/Documentation/ramoops.txt
> index 197ad59..69b3cac 100644
> --- a/Documentation/ramoops.txt
> +++ b/Documentation/ramoops.txt
> @@ -102,9 +102,7 @@ related hangs. The functions call chain log is stored in a "ftrace-ramoops"
> file. Here is an example of usage:
>
> # mount -t debugfs debugfs /sys/kernel/debug/
> - # cd /sys/kernel/debug/tracing
> - # echo function > current_tracer
> - # echo 1 > options/func_pstore
> + # echo 1 > /sys/kernel/debug/pstore/record_ftrace
> # reboot -f
> [...]
> # mount -t pstore pstore /mnt/
> diff --git a/fs/pstore/Kconfig b/fs/pstore/Kconfig
> index d39bb5c..ca71db6 100644
> --- a/fs/pstore/Kconfig
> +++ b/fs/pstore/Kconfig
> @@ -23,6 +23,7 @@ config PSTORE_FTRACE
> bool "Persistent function tracer"
> depends on PSTORE
> depends on FUNCTION_TRACER
> + depends on DEBUG_FS
> help
> With this option kernel traces function calls into a persistent
> ram buffer that can be decoded and dumped after reboot through
> diff --git a/fs/pstore/ftrace.c b/fs/pstore/ftrace.c
> index a130d48..824be81 100644
> --- a/fs/pstore/ftrace.c
> +++ b/fs/pstore/ftrace.c
> @@ -17,19 +17,111 @@
> #include <linux/percpu.h>
> #include <linux/smp.h>
> #include <linux/atomic.h>
> +#include <linux/types.h>
> +#include <linux/mutex.h>
> +#include <linux/ftrace.h>
> +#include <linux/fs.h>
> +#include <linux/debugfs.h>
> +#include <linux/err.h>
> #include <asm/barrier.h>
> #include "internal.h"
>
> -void notrace pstore_ftrace_call(unsigned long ip, unsigned long parent_ip)
> +static void notrace pstore_ftrace_call(unsigned long ip,
> + unsigned long parent_ip)
> {
> + unsigned long flags;
> struct pstore_ftrace_record rec = {};
>
> + if (unlikely(!ftrace_enabled))
> + return;
You don't need this check. The ftrace_enabled is internal to ftrace and
the users shouldn't care. If we disable ftrace, the callback shouldn't
be executed. If it is, that's our fault ;-)
> if (unlikely(oops_in_progress))
> return;
>
> + local_irq_save(flags);
> +
> rec.ip = ip;
> rec.parent_ip = parent_ip;
> pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());
> psinfo->write_buf(PSTORE_TYPE_FTRACE, 0, NULL, 0, (void *)&rec,
> sizeof(rec), psinfo);
> +
> + local_irq_restore(flags);
> +}
> +
> +static struct ftrace_ops pstore_ftrace_ops __read_mostly = {
> + .func = pstore_ftrace_call,
> +};
> +
> +static DEFINE_MUTEX(pstore_ftrace_lock);
> +static bool pstore_ftrace_enabled;
> +
> +static ssize_t pstore_ftrace_knob_write(struct file *f, const char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + u8 on;
> + int err;
> +
> + err = kstrtou8_from_user(buf, count, 2, &on);
> + if (err)
> + return err;
> +
> + mutex_lock(&pstore_ftrace_lock);
> +
> + if (!on ^ pstore_ftrace_enabled)
> + goto out;
> + pstore_ftrace_enabled = on;
> +
> + if (on)
> + register_ftrace_function(&pstore_ftrace_ops);
You might want to check the return value of this.
-- Steve
> + else
> + unregister_ftrace_function(&pstore_ftrace_ops);
> +out:
> + mutex_unlock(&pstore_ftrace_lock);
> +
> + return count;
> +}
> +
> +static ssize_t pstore_ftrace_knob_read(struct file *f, char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + char val[] = { '0' + pstore_ftrace_enabled, '\n' };
> +
> + return simple_read_from_buffer(buf, count, ppos, val, sizeof(val));
> +}
> +
> +static const struct file_operations pstore_knob_fops = {
> + .open = simple_open,
> + .read = pstore_ftrace_knob_read,
> + .write = pstore_ftrace_knob_write,
> +};
> +
> +void pstore_register_ftrace(void)
> +{
> + struct dentry *dir;
> + struct dentry *file;
> + int err;
> +
> + if (!psinfo->write_buf)
> + return;
> +
> + dir = debugfs_create_dir("pstore", NULL);
> + if (IS_ERR_OR_NULL(dir)) {
> + err = PTR_ERR(dir);
> + pr_err("%s: unable to create pstore debugfs: %d\n",
> + __func__, err);
> + return;
> + }
> +
> + file = debugfs_create_file("record_ftrace", 0600, dir, NULL,
> + &pstore_knob_fops);
> + if (IS_ERR_OR_NULL(file)) {
> + err = PTR_ERR(file);
> + pr_err("%s: unable to create pstore/ftrace file: %d\n",
> + __func__, err);
> + goto err_file;
> + }
> +
> + return;
> +err_file:
> + debugfs_remove(dir);
> }
--
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