csky: Fixup futex SMP implementation

Arnd said:
I would guess that for csky, this is a mistake, as the architecture
is fairly new and should be able to implement it.

Guo reply:
The c610, c807, c810 don't support SMP, so futex_cmpxchg_enabled = 1
with asm-generic's implementation.
For c860, there is no HAVE_FUTEX_CMPXCHG and cmpxchg_inatomic/inuser
implementation, so futex_cmpxchg_enabled = 0.

Thx for point it out, we'll implement cmpxchg_inatomic/inuser for
C860 and still use asm-generic for non-smp CPUs.

LTP test:
futex_wait01    1  TPASS  :  futex_wait(): errno=ETIMEDOUT(110): Connection timed out
futex_wait01    2  TPASS  :  futex_wait(): errno=EAGAIN/EWOULDBLOCK(11): Resource temporarily unavailable
futex_wait01    3  TPASS  :  futex_wait(): errno=ETIMEDOUT(110): Connection timed out
futex_wait01    4  TPASS  :  futex_wait(): errno=EAGAIN/EWOULDBLOCK(11): Resource temporarily unavailable
futex_wait02    1  TPASS  :  futex_wait() woken up
futex_wait03    1  TPASS  :  futex_wait() woken up
futex_wait04    1  TPASS  :  futex_wait() returned -1: errno=EAGAIN/EWOULDBLOCK(11): Resource temporarily unavailable

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Cc: Arnd Bergmann <arnd@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/lkml/CAK8P3a3+WaQNyJ6Za2qfu6=0mBgU1hApnRXrdp1b1=P7wwyRUg@mail.gmail.com/

diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
index 21b2ab099c8bd18593d6cee302c8916c4994001f..c74a8e2e85496eebe06c7043bfd4edb540e0f894 100644 (file)
--- a/arch/csky/Kconfig
+++ b/arch/csky/Kconfig
@@ -48,6 +48,7 @@ config CSKY
        select HAVE_FUNCTION_TRACER
        select HAVE_FUNCTION_GRAPH_TRACER
        select HAVE_FUNCTION_ERROR_INJECTION
+       select HAVE_FUTEX_CMPXCHG if FUTEX && SMP
        select HAVE_FTRACE_MCOUNT_RECORD
        select HAVE_KERNEL_GZIP
        select HAVE_KERNEL_LZO

diff --git a/arch/csky/include/asm/futex.h b/arch/csky/include/asm/futex.h
new file mode 100644 (file)
index 0000000..6cfd312
--- /dev/null
+++ b/arch/csky/include/asm/futex.h
@@ -0,0 +1,121 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __ASM_CSKY_FUTEX_H
+#define __ASM_CSKY_FUTEX_H
+
+#ifndef CONFIG_SMP
+#include <asm-generic/futex.h>
+#else
+#include <linux/atomic.h>
+#include <linux/futex.h>
+#include <linux/uaccess.h>
+#include <linux/errno.h>
+
+#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg)             \
+{                                                                      \
+       u32 tmp;                                                        \
+                                                                       \
+       __atomic_pre_full_fence();                                      \
+                                                                       \
+       __asm__ __volatile__ (                                          \
+       "1:     ldex.w  %[ov], %[u]                     \n"             \
+       "       "insn"                                  \n"             \
+       "2:     stex.w  %[t], %[u]                      \n"             \
+       "       bez     %[t], 1b                        \n"             \
+       "       br      4f                              \n"             \
+       "3:     mov     %[r], %[e]                      \n"             \
+       "4:                                             \n"             \
+       "       .section __ex_table,\"a\"               \n"             \
+       "       .balign 4                               \n"             \
+       "       .long   1b, 3b                          \n"             \
+       "       .long   2b, 3b                          \n"             \
+       "       .previous                               \n"             \
+       : [r] "+r" (ret), [ov] "=&r" (oldval),                          \
+         [u] "+m" (*uaddr), [t] "=&r" (tmp)                            \
+       : [op] "Jr" (oparg), [e] "jr" (-EFAULT)                         \
+       : "memory");                                                    \
+                                                                       \
+       __atomic_post_full_fence();                                     \
+}
+
+static inline int
+arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
+{
+       int oldval = 0, ret = 0;
+
+       if (!access_ok(uaddr, sizeof(u32)))
+               return -EFAULT;
+
+       switch (op) {
+       case FUTEX_OP_SET:
+               __futex_atomic_op("mov %[t], %[ov]",
+                                 ret, oldval, uaddr, oparg);
+               break;
+       case FUTEX_OP_ADD:
+               __futex_atomic_op("add %[t], %[ov], %[op]",
+                                 ret, oldval, uaddr, oparg);
+               break;
+       case FUTEX_OP_OR:
+               __futex_atomic_op("or %[t], %[ov], %[op]",
+                                 ret, oldval, uaddr, oparg);
+               break;
+       case FUTEX_OP_ANDN:
+               __futex_atomic_op("and %[t], %[ov], %[op]",
+                                 ret, oldval, uaddr, ~oparg);
+               break;
+       case FUTEX_OP_XOR:
+               __futex_atomic_op("xor %[t], %[ov], %[op]",
+                                 ret, oldval, uaddr, oparg);
+               break;
+       default:
+               ret = -ENOSYS;
+       }
+
+       if (!ret)
+               *oval = oldval;
+
+       return ret;
+}
+
+
+
+static inline int
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
+                             u32 oldval, u32 newval)
+{
+       int ret = 0;
+       u32 val, tmp;
+
+       if (!access_ok(uaddr, sizeof(u32)))
+               return -EFAULT;
+
+       __atomic_pre_full_fence();
+
+       __asm__ __volatile__ (
+       "1:     ldex.w  %[v], %[u]                      \n"
+       "       cmpne   %[v], %[ov]                     \n"
+       "       bt      4f                              \n"
+       "       mov     %[t], %[nv]                     \n"
+       "2:     stex.w  %[t], %[u]                      \n"
+       "       bez     %[t], 1b                        \n"
+       "       br      4f                              \n"
+       "3:     mov     %[r], %[e]                      \n"
+       "4:                                             \n"
+       "       .section __ex_table,\"a\"               \n"
+       "       .balign 4                               \n"
+       "       .long   1b, 3b                          \n"
+       "       .long   2b, 3b                          \n"
+       "       .previous                               \n"
+       : [r] "+r" (ret), [v] "=&r" (val), [u] "+m" (*uaddr),
+         [t] "=&r" (tmp)
+       : [ov] "Jr" (oldval), [nv] "Jr" (newval), [e] "Jr" (-EFAULT)
+       : "memory");
+
+       __atomic_post_full_fence();
+
+       *uval = val;
+       return ret;
+}
+
+#endif /* CONFIG_SMP */
+#endif /* __ASM_CSKY_FUTEX_H */