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| author | Michael Ellerman <mpe@ellerman.id.au> | 2017-07-14 14:49:41 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-07-14 15:05:13 -0700 |
| commit | ffba19ccae8d98beb0a17345a0b1ee9e415b23b8 (patch) | |
| tree | 296a447d459113fb7fb12c25c238409c542b9485 /lib/atomic64_test.c | |
| parent | 37511fb5c91db93d8bd6e3f52f86e5a7ff7cfcdf (diff) | |
| download | lwn-ffba19ccae8d98beb0a17345a0b1ee9e415b23b8.tar.gz lwn-ffba19ccae8d98beb0a17345a0b1ee9e415b23b8.zip | |
lib/atomic64_test.c: add a test that atomic64_inc_not_zero() returns an int
atomic64_inc_not_zero() returns a "truth value" which in C is
traditionally an int. That means callers are likely to expect the
result will fit in an int.
If an implementation returns a "true" value which does not fit in an
int, then there's a possibility that callers will truncate it when they
store it in an int.
In fact this happened in practice, see commit 966d2b04e070
("percpu-refcount: fix reference leak during percpu-atomic transition").
So add a test that the result fits in an int, even when the input
doesn't. This catches the case where an implementation just passes the
non-zero input value out as the result.
Link: http://lkml.kernel.org/r/1499775133-1231-1-git-send-email-mpe@ellerman.id.au
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: Douglas Miller <dougmill@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/atomic64_test.c')
| -rw-r--r-- | lib/atomic64_test.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/lib/atomic64_test.c b/lib/atomic64_test.c index fd70c0e0e673..62ab629f51ca 100644 --- a/lib/atomic64_test.c +++ b/lib/atomic64_test.c @@ -153,8 +153,10 @@ static __init void test_atomic64(void) long long v0 = 0xaaa31337c001d00dLL; long long v1 = 0xdeadbeefdeafcafeLL; long long v2 = 0xfaceabadf00df001LL; + long long v3 = 0x8000000000000000LL; long long onestwos = 0x1111111122222222LL; long long one = 1LL; + int r_int; atomic64_t v = ATOMIC64_INIT(v0); long long r = v0; @@ -240,6 +242,11 @@ static __init void test_atomic64(void) BUG_ON(!atomic64_inc_not_zero(&v)); r += one; BUG_ON(v.counter != r); + + /* Confirm the return value fits in an int, even if the value doesn't */ + INIT(v3); + r_int = atomic64_inc_not_zero(&v); + BUG_ON(!r_int); } static __init int test_atomics_init(void) |