Hello.
Maarten Lankhorst wrote:
> if it's broken for your compiler, please add a bool use_ww_ctx or something
> to __mutex_lock_common that's set directly instead, the __builtin_constant_p
> trick
> might be too gcc version specific.
I see. I tested that both gcc 3.x and gcc 4.x can generate bootable kernel
using below fix.
----------
>From f71fb89bccaa7ed5b3a14e735a1b9cc1a0e7112d Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
Date: Sun, 8 Sep 2013 20:37:19 +0900
Subject: [PATCH] mutex: Avoid gcc version dependent __builtin_constant_p()
usage.
Commit 040a0a37 "mutex: Add support for wound/wait style locks" used
"!__builtin_constant_p(p == NULL)" but gcc 3.x cannot handle such expression
correctly, leading to boot failure when built with CONFIG_DEBUG_MUTEXES=y.
Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
Cc: <sta...@kernel.org> [3.11+]
---
kernel/mutex.c | 9 +++++----
1 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/kernel/mutex.c b/kernel/mutex.c
index a52ee7bb..2e7984e 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -414,6 +414,7 @@ __mutex_lock_common(struct mutex *lock, long state,
unsigned int subclass,
struct mutex_waiter waiter;
unsigned long flags;
int ret;
+ const bool use_ww_ctx = !!ww_ctx;
preempt_disable();
mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
@@ -448,7 +449,7 @@ __mutex_lock_common(struct mutex *lock, long state,
unsigned int subclass,
struct task_struct *owner;
struct mspin_node node;
- if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired >
0) {
+ if (use_ww_ctx && ww_ctx->acquired > 0) {
struct ww_mutex *ww;
ww = container_of(lock, struct ww_mutex, base);
@@ -478,7 +479,7 @@ __mutex_lock_common(struct mutex *lock, long state,
unsigned int subclass,
if ((atomic_read(&lock->count) == 1) &&
(atomic_cmpxchg(&lock->count, 1, 0) == 1)) {
lock_acquired(&lock->dep_map, ip);
- if (!__builtin_constant_p(ww_ctx == NULL)) {
+ if (use_ww_ctx) {
struct ww_mutex *ww;
ww = container_of(lock, struct ww_mutex, base);
@@ -548,7 +549,7 @@ slowpath:
goto err;
}
- if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired >
0) {
+ if (use_ww_ctx && ww_ctx->acquired > 0) {
ret = __mutex_lock_check_stamp(lock, ww_ctx);
if (ret)
goto err;
@@ -568,7 +569,7 @@ done:
mutex_remove_waiter(lock, &waiter, current_thread_info());
mutex_set_owner(lock);
- if (!__builtin_constant_p(ww_ctx == NULL)) {
+ if (use_ww_ctx) {
struct ww_mutex *ww = container_of(lock,
struct ww_mutex,
base);
--
1.7.8
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