On Wed, Jul 18, 2012 at 12:30:52PM -0700, Anton Vorontsov wrote:
> With this patch we no longer reuse function tracer infrastructure, now
> we register our own tracer back-end via a debugfs knob.
>
> It's a bit more code, but that is the only downside. On the bright side we
> have:
>
> - Ability to make persistent_ram module removable (when needed, we can
> move ftrace_ops struct into a module). Note that persistent_ram is still
> not removable for other reasons, but with this patch it's just one
> thing less to worry about;
>
> - Pstore part is more isolated from the generic function tracer. We tried
> it already by registering our own tracer in available_tracers, but that
> way we're loosing ability to see the traces while we record them to
> pstore. This solution is somewhere in the middle: we only register
> "internal ftracer" back-end, but not the "front-end";
>
> - When there is only pstore tracing enabled, the kernel will only write
> to the pstore buffer, omitting function tracer buffer (which, of course,
> still can be enabled via 'echo function > current_tracer').
>
> Suggested-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Signed-off-by: Anton Vorontsov <anton.vorontsov@xxxxxxxxxx>
> ---
Hi Steven,
Unless there are any issues, may I take the patch via linux-pstore.git
tree?
Thanks!
> Documentation/ramoops.txt | 4 +-
> fs/pstore/Kconfig | 1 +
> fs/pstore/ftrace.c | 96 +++++++++++++++++++++++++++++++++++++++-
> fs/pstore/internal.h | 6 +++
> fs/pstore/platform.c | 1 +
> include/linux/pstore.h | 8 ----
> kernel/trace/trace_functions.c | 15 +------
> 7 files changed, 105 insertions(+), 26 deletions(-)
>
> 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..2d57e1a 100644
> --- a/fs/pstore/ftrace.c
> +++ b/fs/pstore/ftrace.c
> @@ -17,19 +17,113 @@
> #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 <linux/cache.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(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;
> + ssize_t ret;
> +
> + ret = kstrtou8_from_user(buf, count, 2, &on);
> + if (ret)
> + return ret;
> +
> + mutex_lock(&pstore_ftrace_lock);
> +
> + if (!on ^ pstore_ftrace_enabled)
> + goto out;
> +
> + if (on)
> + ret = register_ftrace_function(&pstore_ftrace_ops);
> + else
> + ret = unregister_ftrace_function(&pstore_ftrace_ops);
> + if (ret) {
> + pr_err("%s: unable to %sregister ftrace ops: %zd\n",
> + __func__, on ? "" : "un", ret);
> + goto err;
> + }
> +
> + pstore_ftrace_enabled = on;
> +out:
> + ret = count;
> +err:
> + mutex_unlock(&pstore_ftrace_lock);
> +
> + return ret;
> +}
> +
> +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;
> +
> + if (!psinfo->write_buf)
> + return;
> +
> + dir = debugfs_create_dir("pstore", NULL);
> + if (!dir) {
> + pr_err("%s: unable to create pstore directory\n", __func__);
> + return;
> + }
> +
> + file = debugfs_create_file("record_ftrace", 0600, dir, NULL,
> + &pstore_knob_fops);
> + if (!file) {
> + pr_err("%s: unable to create record_ftrace file\n", __func__);
> + goto err_file;
> + }
> +
> + return;
> +err_file:
> + debugfs_remove(dir);
> }
> diff --git a/fs/pstore/internal.h b/fs/pstore/internal.h
> index 0d0d3b7..4847f58 100644
> --- a/fs/pstore/internal.h
> +++ b/fs/pstore/internal.h
> @@ -39,6 +39,12 @@ pstore_ftrace_decode_cpu(struct pstore_ftrace_record *rec)
> #endif
> }
>
> +#ifdef CONFIG_PSTORE_FTRACE
> +extern void pstore_register_ftrace(void);
> +#else
> +static inline void pstore_register_ftrace(void) {}
> +#endif
> +
> extern struct pstore_info *psinfo;
>
> extern void pstore_set_kmsg_bytes(int);
> diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
> index 29996e8..6c23eab 100644
> --- a/fs/pstore/platform.c
> +++ b/fs/pstore/platform.c
> @@ -236,6 +236,7 @@ int pstore_register(struct pstore_info *psi)
>
> kmsg_dump_register(&pstore_dumper);
> pstore_register_console();
> + pstore_register_ftrace();
>
> if (pstore_update_ms >= 0) {
> pstore_timer.expires = jiffies +
> diff --git a/include/linux/pstore.h b/include/linux/pstore.h
> index c892587..ee3034a 100644
> --- a/include/linux/pstore.h
> +++ b/include/linux/pstore.h
> @@ -64,14 +64,6 @@ struct pstore_info {
> void *data;
> };
>
> -
> -#ifdef CONFIG_PSTORE_FTRACE
> -extern void pstore_ftrace_call(unsigned long ip, unsigned long parent_ip);
> -#else
> -static inline void pstore_ftrace_call(unsigned long ip, unsigned long parent_ip)
> -{ }
> -#endif
> -
> #ifdef CONFIG_PSTORE
> extern int pstore_register(struct pstore_info *);
> #else
> diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
> index a426f41..0ad83e3 100644
> --- a/kernel/trace/trace_functions.c
> +++ b/kernel/trace/trace_functions.c
> @@ -13,7 +13,6 @@
> #include <linux/debugfs.h>
> #include <linux/uaccess.h>
> #include <linux/ftrace.h>
> -#include <linux/pstore.h>
> #include <linux/fs.h>
>
> #include "trace.h"
> @@ -75,10 +74,9 @@ function_trace_call_preempt_only(unsigned long ip, unsigned long parent_ip)
> preempt_enable_notrace();
> }
>
> -/* Our two options */
> +/* Our option */
> enum {
> TRACE_FUNC_OPT_STACK = 0x1,
> - TRACE_FUNC_OPT_PSTORE = 0x2,
> };
>
> static struct tracer_flags func_flags;
> @@ -106,12 +104,6 @@ function_trace_call(unsigned long ip, unsigned long parent_ip)
> disabled = atomic_inc_return(&data->disabled);
>
> if (likely(disabled == 1)) {
> - /*
> - * So far tracing doesn't support multiple buffers, so
> - * we make an explicit call for now.
> - */
> - if (unlikely(func_flags.val & TRACE_FUNC_OPT_PSTORE))
> - pstore_ftrace_call(ip, parent_ip);
> pc = preempt_count();
> trace_function(tr, ip, parent_ip, flags, pc);
> }
> @@ -177,9 +169,6 @@ static struct tracer_opt func_opts[] = {
> #ifdef CONFIG_STACKTRACE
> { TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
> #endif
> -#ifdef CONFIG_PSTORE_FTRACE
> - { TRACER_OPT(func_pstore, TRACE_FUNC_OPT_PSTORE) },
> -#endif
> { } /* Always set a last empty entry */
> };
>
> @@ -232,8 +221,6 @@ static int func_set_flag(u32 old_flags, u32 bit, int set)
> }
>
> break;
> - case TRACE_FUNC_OPT_PSTORE:
> - break;
> default:
> return -EINVAL;
> }
> --
> 1.7.10.4
>
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