linux-kernel - [PATCH 4.19 046/116] ftrace/x86: Anotate text_mutex split between ftrace_arch_code_modify_post_process() and ftrace_arch_code_modify

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Message-Id: <20200401161548.389053638@linuxfoundation.org>
Date:   Wed,  1 Apr 2020 18:17:02 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jiri Kosina <jkosina@...e.cz>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH 4.19 046/116] ftrace/x86: Anotate text_mutex split between ftrace_arch_code_modify_post_process() and ftrace_arch_code_modify_prepare()

From: Jiri Kosina <jkosina@...e.cz>

commit 074376ac0e1d1fcd4fafebca86ee6158e7c20680 upstream.

ftrace_arch_code_modify_prepare() is acquiring text_mutex, while the
corresponding release is happening in ftrace_arch_code_modify_post_process().

This has already been documented in the code, but let's also make the fact
that this is intentional clear to the semantic analysis tools such as sparse.

Link: http://lkml.kernel.org/r/nycvar.YFH.7.76.1906292321170.27227@cbobk.fhfr.pm

Fixes: 39611265edc1a ("ftrace/x86: Add a comment to why we take text_mutex in ftrace_arch_code_modify_prepare()")
Fixes: d5b844a2cf507 ("ftrace/x86: Remove possible deadlock between register_kprobe() and ftrace_run_update_code()")
Signed-off-by: Jiri Kosina <jkosina@...e.cz>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Cc: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kernel/ftrace.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -35,6 +35,7 @@
 #ifdef CONFIG_DYNAMIC_FTRACE
 
 int ftrace_arch_code_modify_prepare(void)
+    __acquires(&text_mutex)
 {
 	mutex_lock(&text_mutex);
 	set_kernel_text_rw();
@@ -43,6 +44,7 @@ int ftrace_arch_code_modify_prepare(void
 }
 
 int ftrace_arch_code_modify_post_process(void)
+    __releases(&text_mutex)
 {
 	set_all_modules_text_ro();
 	set_kernel_text_ro();