Re: [PATCH 1/2 v4] rseq/membarrier: add MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ

[kernel test robot]

Hi Peter,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on kselftest/next]
[also build test ERROR on tip/sched/core linux/master linus/master v5.9-rc2 next-20200826]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Peter-Oskolkov/rseq-membarrier-add-MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ/20200827-024952
base:   https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest.git next
config: powerpc64-randconfig-r001-20200826 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 7cfcecece0e0430937cf529ce74d3a071a4dedc6)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install powerpc64 cross compiling tool for clang build
        # apt-get install binutils-powerpc64-linux-gnu
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=powerpc64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All errors (new ones prefixed by >>):

>> kernel/sched/membarrier.c:379:1: error: conflicting types for 'sys_membarrier'
   SYSCALL_DEFINE3(membarrier, int, cmd, int, flags, int, cpu_id)
   ^
   include/linux/syscalls.h:215:36: note: expanded from macro 'SYSCALL_DEFINE3'
   #define SYSCALL_DEFINE3(name, ...) SYSCALL_DEFINEx(3, _##name, __VA_ARGS__)
                                      ^
   include/linux/syscalls.h:224:2: note: expanded from macro 'SYSCALL_DEFINEx'
           __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
           ^
   include/linux/syscalls.h:238:18: note: expanded from macro '__SYSCALL_DEFINEx'
           asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))       \
                           ^
   <scratch space>:7:1: note: expanded from here
   sys_membarrier
   ^
   include/linux/syscalls.h:977:17: note: previous declaration is here
   asmlinkage long sys_membarrier(int cmd, int flags);
                   ^
   1 error generated.

# https://github.com/0day-ci/linux/commit/41ee0f192c40af25a53abea1610a9ea4852cf0f4
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Peter-Oskolkov/rseq-membarrier-add-MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ/20200827-024952
git checkout 41ee0f192c40af25a53abea1610a9ea4852cf0f4
vim +/sys_membarrier +379 kernel/sched/membarrier.c

   342	
   343	/**
   344	 * sys_membarrier - issue memory barriers on a set of threads
   345	 * @cmd:    Takes command values defined in enum membarrier_cmd.
   346	 * @flags:  Currently needs to be 0 for all commands other than
   347	 *          MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ: in the latter
   348	 *          case it can be MEMBARRIER_CMD_FLAG_CPU, indicating that @cpu_id
   349	 *          contains the CPU on which to interrupt (= restart)
   350	 *          the RSEQ critical section.
   351	 * @cpu_id: if @flags == MEMBARRIER_CMD_FLAG_CPU, indicates the cpu on which
   352	 *          RSEQ CS should be interrupted (@cmd must be
   353	 *          MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ).
   354	 *
   355	 * If this system call is not implemented, -ENOSYS is returned. If the
   356	 * command specified does not exist, not available on the running
   357	 * kernel, or if the command argument is invalid, this system call
   358	 * returns -EINVAL. For a given command, with flags argument set to 0,
   359	 * if this system call returns -ENOSYS or -EINVAL, it is guaranteed to
   360	 * always return the same value until reboot. In addition, it can return
   361	 * -ENOMEM if there is not enough memory available to perform the system
   362	 * call.
   363	 *
   364	 * All memory accesses performed in program order from each targeted thread
   365	 * is guaranteed to be ordered with respect to sys_membarrier(). If we use
   366	 * the semantic "barrier()" to represent a compiler barrier forcing memory
   367	 * accesses to be performed in program order across the barrier, and
   368	 * smp_mb() to represent explicit memory barriers forcing full memory
   369	 * ordering across the barrier, we have the following ordering table for
   370	 * each pair of barrier(), sys_membarrier() and smp_mb():
   371	 *
   372	 * The pair ordering is detailed as (O: ordered, X: not ordered):
   373	 *
   374	 *                        barrier()   smp_mb() sys_membarrier()
   375	 *        barrier()          X           X            O
   376	 *        smp_mb()           X           O            O
   377	 *        sys_membarrier()   O           O            O
   378	 */
 > 379	SYSCALL_DEFINE3(membarrier, int, cmd, int, flags, int, cpu_id)

---
0-DAY CI Kernel Test Service, Intel Corporation
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