# git rev-parse -q --verify a6fcdbf95d7907bc5d5a669adb86e6bda72d738b^{commit}
a6fcdbf95d7907bc5d5a669adb86e6bda72d738b
already have revision, skipping fetch
# git checkout -q -f -B kisskb a6fcdbf95d7907bc5d5a669adb86e6bda72d738b
# git clean -qxdf
# < git log -1
# commit a6fcdbf95d7907bc5d5a669adb86e6bda72d738b
# Author: Reza Arbab <arbab@linux.ibm.com>
# Date:   Thu Aug 2 23:03:36 2018 -0500
# 
#     powerpc/powernv: Fix concurrency issue with npu->mmio_atsd_usage
#     
#     We've encountered a performance issue when multiple processors stress
#     {get,put}_mmio_atsd_reg(). These functions contend for
#     mmio_atsd_usage, an unsigned long used as a bitmask.
#     
#     The accesses to mmio_atsd_usage are done using test_and_set_bit_lock()
#     and clear_bit_unlock(). As implemented, both of these will require
#     a (successful) stwcx to that same cache line.
#     
#     What we end up with is thread A, attempting to unlock, being slowed by
#     other threads repeatedly attempting to lock. A's stwcx instructions
#     fail and retry because the memory reservation is lost every time a
#     different thread beats it to the punch.
#     
#     There may be a long-term way to fix this at a larger scale, but for
#     now resolve the immediate problem by gating our call to
#     test_and_set_bit_lock() with one to test_bit(), which is obviously
#     implemented without using a store.
#     
#     Fixes: 1ab66d1fbada ("powerpc/powernv: Introduce address translation services for Nvlink2")
#     Signed-off-by: Reza Arbab <arbab@linux.ibm.com>
#     Acked-by: Alistair Popple <alistair@popple.id.au>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
# < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/hppa-linux/bin/hppa-linux-gcc --version
# < git log --format=%s --max-count=1 a6fcdbf95d7907bc5d5a669adb86e6bda72d738b
# < make -s -j 48 ARCH=parisc O=/kisskb/build/powerpc-next_parisc-defconfig_parisc CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/hppa-linux/bin/hppa-linux-  defconfig
# make -s -j 48 ARCH=parisc O=/kisskb/build/powerpc-next_parisc-defconfig_parisc CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/hppa-linux/bin/hppa-linux-  
/kisskb/src/net/Makefile:24: CC cannot link executables. Skipping bpfilter.
<stdin>:1335:2: warning: #warning syscall rseq not implemented [-Wcpp]
/kisskb/src/net/Makefile:24: CC cannot link executables. Skipping bpfilter.
In function 'kernfs_get_target_path',
    inlined from 'kernfs_getlink.isra.0' at /kisskb/src/fs/kernfs/symlink.c:109:10,
    inlined from 'kernfs_iop_get_link.part.1' at /kisskb/src/fs/kernfs/symlink.c:127:10,
    inlined from 'kernfs_iop_get_link':
/kisskb/src/fs/kernfs/symlink.c:91:3: warning: 'strncpy' output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation]
   strncpy(s + len, kn->name, slen);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/kisskb/src/fs/kernfs/symlink.c: In function 'kernfs_iop_get_link':
/kisskb/src/fs/kernfs/symlink.c:88:14: note: length computed here
   int slen = strlen(kn->name);
              ^~~~~~~~~~~~~~~~
/kisskb/src/crypto/ablkcipher.c: In function 'crypto_ablkcipher_report':
/kisskb/src/crypto/ablkcipher.c:374:2: warning: 'strncpy' specified bound 64 equals destination size [-Wstringop-truncation]
  strncpy(rblkcipher.geniv, alg->cra_ablkcipher.geniv ?: "<default>",
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   sizeof(rblkcipher.geniv));
   ~~~~~~~~~~~~~~~~~~~~~~~~~
/kisskb/src/crypto/ablkcipher.c: In function 'crypto_givcipher_report':
/kisskb/src/crypto/ablkcipher.c:448:2: warning: 'strncpy' specified bound 64 equals destination size [-Wstringop-truncation]
  strncpy(rblkcipher.geniv, alg->cra_ablkcipher.geniv ?: "<built-in>",
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   sizeof(rblkcipher.geniv));
   ~~~~~~~~~~~~~~~~~~~~~~~~~
/kisskb/src/crypto/blkcipher.c: In function 'crypto_blkcipher_report':
/kisskb/src/crypto/blkcipher.c:513:2: warning: 'strncpy' specified bound 64 equals destination size [-Wstringop-truncation]
  strncpy(rblkcipher.geniv, alg->cra_blkcipher.geniv ?: "<default>",
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   sizeof(rblkcipher.geniv));
   ~~~~~~~~~~~~~~~~~~~~~~~~~
/kisskb/src/fs/ext4/super.c: In function '__save_error_info.isra.5':
/kisskb/src/fs/ext4/super.c:326:2: warning: 'strncpy' specified bound 32 equals destination size [-Wstringop-truncation]
  strncpy(es->s_last_error_func, func, sizeof(es->s_last_error_func));
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/kisskb/src/fs/ext4/super.c:330:3: warning: 'strncpy' specified bound 32 equals destination size [-Wstringop-truncation]
   strncpy(es->s_first_error_func, func,
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    sizeof(es->s_first_error_func));
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In function 'fill_kobj_path',
    inlined from 'kobject_get_path' at /kisskb/src/lib/kobject.c:155:2:
/kisskb/src/lib/kobject.c:128:3: warning: 'strncpy' output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation]
   strncpy(path + length, kobject_name(parent), cur);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/kisskb/src/lib/kobject.c: In function 'kobject_get_path':
/kisskb/src/lib/kobject.c:125:13: note: length computed here
   int cur = strlen(kobject_name(parent));
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
Completed OK
# rm -rf /kisskb/build/powerpc-next_parisc-defconfig_parisc
# Build took: 0:01:03.638391