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bitops: add xor_unlock_is_negative_byte()

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Replace clear_bit_and_unlock_is_negative_byte() with
xor_unlock_is_negative_byte().  We have a few places that like to lock a
folio, set a flag and unlock it again.  Allow for the possibility of
combining the latter two operations for efficiency.  We are guaranteed
that the caller holds the lock, so it is safe to unlock it with the xor. 
The caller must guarantee that nobody else will set the flag without
holding the lock; it is not safe to do this with the PG_dirty flag, for
example.

Link: https://lkml.kernel.org/r/20231004165317.1061855-8-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle)
2023-10-04 17:53:07 +01:00
committed by Andrew Morton
parent 7a4847e54c
commit 247dbcdbf7
8 changed files with 47 additions and 57 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
kernel/kcsan/kcsan_test.c
View File

@@ -700,10 +700,10 @@ static void test_barrier_nothreads(struct kunit *test)
KCSAN_EXPECT_RW_BARRIER(mutex_lock(&test_mutex), false);
KCSAN_EXPECT_RW_BARRIER(mutex_unlock(&test_mutex), true);
#ifdef clear_bit_unlock_is_negative_byte
KCSAN_EXPECT_READ_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var), true);
KCSAN_EXPECT_WRITE_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var), true);
KCSAN_EXPECT_RW_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var), true);
#ifdef xor_unlock_is_negative_byte
KCSAN_EXPECT_READ_BARRIER(xor_unlock_is_negative_byte(1, &test_var), true);
KCSAN_EXPECT_WRITE_BARRIER(xor_unlock_is_negative_byte(1, &test_var), true);
KCSAN_EXPECT_RW_BARRIER(xor_unlock_is_negative_byte(1, &test_var), true);
#endif
kcsan_nestable_atomic_end();
}

8
kernel/kcsan/selftest.c
View File

@@ -228,10 +228,10 @@ static bool __init test_barrier(void)
spin_lock(&test_spinlock);
KCSAN_CHECK_RW_BARRIER(spin_unlock(&test_spinlock));
#ifdef clear_bit_unlock_is_negative_byte
KCSAN_CHECK_RW_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
KCSAN_CHECK_READ_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
KCSAN_CHECK_WRITE_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
#ifdef xor_unlock_is_negative_byte
KCSAN_CHECK_RW_BARRIER(xor_unlock_is_negative_byte(1, &test_var));
KCSAN_CHECK_READ_BARRIER(xor_unlock_is_negative_byte(1, &test_var));
KCSAN_CHECK_WRITE_BARRIER(xor_unlock_is_negative_byte(1, &test_var));
#endif
kcsan_nestable_atomic_end();