refcount: Create unchecked atomic_t implementation

locking/refcount: Create unchecked atomic_t implementation

Quoted 1 line · tip-bot for Kees Cook

locking/refcount: Create unchecked atomic_t implementation

This seems to do only half the job. Here's the rest.

---
Subject: locking/refcount: Finish unchecked atomic_t implementation

For some reason the unchecked atomic_t implementation stopped half-way through, complete it it.

Fixes fd25d19f6b8d ("locking/refcount: Create unchecked atomic_t implementation")

Signed-off-by Peter Zijlstra (Intel) <[email protected]>

---
 include/linux/refcount.h | 35 ++++++++++++++++++++++++++++++-----
 lib/Makefile             |  7 +++----
 lib/refcount.c           |  3 ---
 3 files changed, 33 insertions(+), 12 deletions(-)

include/linux/refcount.h +30 -5

index 48b7c9c68c4d..ef714e4347d9 100644
@@ -52,10 +52,17 @@ extern __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r);
 
 extern __must_check bool refcount_dec_and_test(refcount_t *r);
 extern void refcount_dec(refcount_t *r);
+
+extern __must_check bool refcount_dec_if_one(refcount_t *r);
+extern __must_check bool refcount_dec_not_one(refcount_t *r);
+extern __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock);
+extern __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock);
+
 #else
 # ifdef CONFIG_ARCH_HAS_REFCOUNT
 #  include <asm/refcount.h>
 # else
+
 static inline __must_check bool refcount_add_not_zero(unsigned int i, refcount_t *r)
 {
        return atomic_add_unless(&r->refs, i, 0);

@@ -90,12 +97,30 @@ static inline void refcount_dec(refcount_t *r)
 {
        atomic_dec(&r->refs);
 }
+
+static inline __must_check bool refcount_dec_if_one(refcount_t *r)
+{
+       int val = 1;
+
+       return atomic_try_cmpxchg_release(&r->refs, &val, 0);
+}
+
+static inline __must_check bool refcount_dec_not_one(refcount_t *r)
+{
+       return atomic_add_unless(&r->refs, -1, 1);
+}
+
+static inline __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock)
+{
+       return atomic_dec_and_mutex_lock(&r->refs, lock);
+}
+
+static inline __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock)
+{
+       return atomic_dec_and_lock(&r->refs, lock);
+}
+
 # endif /* !CONFIG_ARCH_HAS_REFCOUNT */
 #endif /* CONFIG_REFCOUNT_FULL */
 
-extern __must_check bool refcount_dec_if_one(refcount_t *r);
-extern __must_check bool refcount_dec_not_one(refcount_t *r);
-extern __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock);
-extern __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock);
-
 #endif /* _LINUX_REFCOUNT_H */

lib/Makefile +3 -4

index 40c18372b301..b96859e69c57 100644
@@ -38,12 +38,11 @@ obj-y += bcd.o div64.o sort.o parser.o debug_locks.o random32.o \
         gcd.o lcm.o list_sort.o uuid.o flex_array.o iov_iter.o clz_ctz.o \
         bsearch.o find_bit.o llist.o memweight.o kfifo.o \
         percpu-refcount.o percpu_ida.o rhashtable.o reciprocal_div.o \
-        once.o refcount.o usercopy.o errseq.o
-obj-y += string_helpers.o
+        once.o usercopy.o errseq.o string_helpers.o hexdump.o kstrtox.o
+
+obj-$(CONFIG_REFCOUNT_FULL) += refcount.o
 obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
-obj-y += hexdump.o
 obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o
-obj-y += kstrtox.o
 obj-$(CONFIG_TEST_BPF) += test_bpf.o
 obj-$(CONFIG_TEST_FIRMWARE) += test_firmware.o
 obj-$(CONFIG_TEST_SYSCTL) += test_sysctl.o

lib/refcount.c +0 -3

index 5d0582a9480c..9f906783987e 100644
@@ -37,8 +37,6 @@
 #include <linux/refcount.h>
 #include <linux/bug.h>
 
-#ifdef CONFIG_REFCOUNT_FULL
-
 /**
  * refcount_add_not_zero - add a value to a refcount unless it is 0
  * @i: the value to add to the refcount

@@ -227,7 +225,6 @@ void refcount_dec(refcount_t *r)
        WARN_ONCE(refcount_dec_and_test(r), "refcount_t: decrement hit 0; leaking memory.\n");
 }
 EXPORT_SYMBOL(refcount_dec);
-#endif /* CONFIG_REFCOUNT_FULL */
 
 /**
  * refcount_dec_if_one - decrement a refcount if it is 1

Quoted 5 lines · Peter Zijlstra

Quoted 1 line · tip-bot for Kees Cook

locking/refcount: Create unchecked atomic_t implementation

This seems to do only half the job. Here's the rest.

Quoted 5 lines

---
Subject: locking/refcount: Finish unchecked atomic_t implementation

For some reason the unchecked atomic_t implementation stopped half-way through, complete it it.

Hmm? The reason is that the implementation of the remaining functions is unchanged between full, unchecked, and x86.

lib/Makefile obj-y += bcd.o div64.o sort.o parser.o debug_locks.o random32.o \ · line 46

Quoted 9 lines · Peter Zijlstra

lib/Makefile +3 -4

-	 once.o refcount.o usercopy.o errseq.o
-obj-y += string_helpers.o
+	 once.o usercopy.o errseq.o string_helpers.o hexdump.o kstrtox.o
+
+obj-$(CONFIG_REFCOUNT_FULL) += refcount.o
 obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
-obj-y += hexdump.o
 obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o
-obj-y += kstrtox.o

File per line so everything is not lumped together even if it is obj-y.

Quoted 12 lines · Alexey Dobriyan

lib/Makefile obj-y += bcd.o div64.o sort.o parser.o debug_locks.o random32.o \ · line 46

Quoted 9 lines · Peter Zijlstra

lib/Makefile +3 -4

-	 once.o refcount.o usercopy.o errseq.o
-obj-y += string_helpers.o
+	 once.o usercopy.o errseq.o string_helpers.o hexdump.o kstrtox.o
+
+obj-$(CONFIG_REFCOUNT_FULL) += refcount.o
 obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
-obj-y += hexdump.o
 obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o
-obj-y += kstrtox.o

File per line so everything is not lumped together even if it is obj-y.

If that is policy mass convert everything and be done with it. Otherwise I'll continue to use the predominant pattern, which in this case is a giant obj-y +=. But mixed stuff is terribly annoying.

It is not a policy, just a "grassroot" movement to give people good example and wait until someone is annoyed enough to mass convert everything. -)

Worked for fs/proc/Makefile .