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Message-ID: <1423806039-61864-1-git-send-email-wangnan0@huawei.com>
Date: Fri, 13 Feb 2015 13:40:39 +0800
From: Wang Nan <wangnan0@...wei.com>
To: <linux@....linux.org.uk>, <tglx@...utronix.de>, <mingo@...hat.com>,
<hpa@...or.com>, <rostedt@...dmis.org>, <ananth@...ibm.com>,
<anil.s.keshavamurthy@...el.com>, <davem@...emloft.net>,
<masami.hiramatsu.pt@...achi.com>, <luto@...capital.net>,
<keescook@...omium.org>, <oleg@...hat.com>, <wangnan0@...wei.com>,
<dave.long@...aro.org>, <tixy@...aro.org>, <nico@...aro.org>,
<yalin.wang2010@...il.com>, <catalin.marinas@....com>,
<Yalin.Wang@...ymobile.com>, <mark.rutland@....com>,
<dave.hansen@...ux.intel.com>, <jkenisto@...ibm.com>,
<anton@...ba.org>, <stefani@...bold.net>, <JBeulich@...e.com>,
<akpm@...ux-foundation.org>, <rusty@...tcorp.com.au>,
<peterz@...radead.org>, <prarit@...hat.com>, <fabf@...net.be>,
<hannes@...xchg.org>
CC: <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>, <lizefan@...wei.com>
Subject: [RFC PATCH v3 09/26] ftrace: allow fixing code update failure by notifier chain.
This patch introduces a notifier chain (ftrace_update_notifier_list) and
ftrace_tryfix_bug(). The goal of this patch is to provide other
subsystem a chance to fix code if they alert ftrace entries before
ftrace_init().
Such subsystems should register a callback with
register_ftrace_update_notifier(). Ftrace will trigger the callback by
ftrace_tryfix_bug() when it fail to alert ftrace entries, instead of
directly fire an ftrace_bug(). It wrapps failure information with
a struct ftrace_update_notifier_info. Subscriber is able to determine
what it trying to do with it.
Subscriber of that notifier chain should return NOTIFY_STOP if it can
deal with the problem, or NOTIFY_DONE to pass it to other. By setting
info->retry it can inform ftrace to retry faild operation.
Signed-off-by: Wang Nan <wangnan0@...wei.com>
---
include/linux/ftrace.h | 30 ++++++++++++++++++++++++++++++
kernel/trace/ftrace.c | 46 ++++++++++++++++++++++++++++++++++++++++------
2 files changed, 70 insertions(+), 6 deletions(-)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index d37ccd8a..98da86d 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -283,6 +283,21 @@ int ftrace_arch_code_modify_post_process(void);
struct dyn_ftrace;
void ftrace_bug(int err, struct dyn_ftrace *rec);
+int ftrace_tryfix(int failed, int enable, struct dyn_ftrace *rec);
+
+#define __ftrace_tryfix_bug(__failed, __enable, __rec, __retry, __trigger)\
+ ({ \
+ int __fix_ret = ftrace_tryfix((__failed), (__enable), (__rec));\
+ __fix_ret = (__fix_ret == -EAGAIN) ? \
+ ({ __retry; }) : \
+ __fix_ret; \
+ if (__fix_ret && (__trigger)) \
+ ftrace_bug(__failed, __rec); \
+ __fix_ret; \
+ })
+
+#define ftrace_tryfix_bug(__failed, __enable, __rec, __retry) \
+ __ftrace_tryfix_bug(__failed, __enable, __rec, __retry, true)
struct seq_file;
@@ -699,10 +714,20 @@ static inline void __ftrace_enabled_restore(int enabled)
# define trace_preempt_off(a0, a1) do { } while (0)
#endif
+struct ftrace_update_notifier_info {
+ struct dyn_ftrace *rec;
+ int errno;
+ int enable;
+
+ /* Filled by subscriber */
+ bool retry;
+};
+
#ifdef CONFIG_FTRACE_MCOUNT_RECORD
extern void ftrace_init(void);
extern void ftrace_init_early(void);
extern int ftrace_process_loc_early(unsigned long ip);
+extern int register_ftrace_update_notifier(struct notifier_block *nb);
#else
static inline void ftrace_init(void) { }
static inline void ftrace_init_early(void) { }
@@ -710,6 +735,11 @@ static inline int ftrace_process_loc_early(unsigned long __unused)
{
return 0;
}
+
+static inline int register_ftrace_update_notifier(struct notifier_block *__unused)
+{
+ return 0;
+}
#endif
/*
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index e39e72a..d75b823 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -112,6 +112,7 @@ ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub;
static struct ftrace_ops global_ops;
static struct ftrace_ops control_ops;
+static ATOMIC_NOTIFIER_HEAD(ftrace_update_notifier_list);
static void ftrace_ops_recurs_func(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct pt_regs *regs);
@@ -1971,6 +1972,28 @@ void ftrace_bug(int failed, struct dyn_ftrace *rec)
}
}
+int ftrace_tryfix(int failed, int enable, struct dyn_ftrace *rec)
+{
+ int notify_result = NOTIFY_DONE;
+ struct ftrace_update_notifier_info info = {
+ .rec = rec,
+ .errno = failed,
+ .enable = enable,
+ .retry = false,
+ };
+
+ notify_result = atomic_notifier_call_chain(
+ &ftrace_update_notifier_list,
+ 0, &info);
+
+ if (notify_result != NOTIFY_STOP)
+ return failed;
+
+ if (info.retry)
+ return -EAGAIN;
+ return 0;
+}
+
static int ftrace_check_record(struct dyn_ftrace *rec, int enable, int update)
{
unsigned long flag = 0UL;
@@ -2298,9 +2321,12 @@ void __weak ftrace_replace_code(int enable)
do_for_each_ftrace_rec(pg, rec) {
failed = __ftrace_replace_code(rec, enable);
if (failed) {
- ftrace_bug(failed, rec);
- /* Stop processing */
- return;
+ failed = ftrace_tryfix_bug(failed, enable, rec,
+ __ftrace_replace_code(rec, enable));
+
+ /* Stop processing if still fail */
+ if (failed)
+ return;
}
} while_for_each_ftrace_rec();
}
@@ -2387,8 +2413,10 @@ ftrace_code_disable(struct module *mod, struct dyn_ftrace *rec)
ret = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
if (ret) {
- ftrace_bug(ret, rec);
- return 0;
+ ret = ftrace_tryfix_bug(ret, 0, rec,
+ ftrace_make_nop(mod, rec, MCOUNT_ADDR));
+ if (ret)
+ return 0;
}
return 1;
}
@@ -2844,7 +2872,8 @@ static int ftrace_update_code(struct module *mod, struct ftrace_page *new_pgs)
if (ftrace_start_up && cnt) {
int failed = __ftrace_replace_code(p, 1);
if (failed)
- ftrace_bug(failed, p);
+ failed = ftrace_tryfix_bug(failed, 1, p,
+ __ftrace_replace_code(p, 1));
}
}
}
@@ -5673,6 +5702,11 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
return ret;
}
+int register_ftrace_update_notifier(struct notifier_block *nb)
+{
+ return atomic_notifier_chain_register(&ftrace_update_notifier_list, nb);
+}
+
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
static struct ftrace_ops graph_ops = {
--
1.8.4
--
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