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Date: Sun, 20 Dec 2020 15:39:21 +0000
From: guoren@...nel.org
To: guoren@...nel.org, arnd@...db.de
Cc: linux-kernel@...r.kernel.org, linux-csky@...r.kernel.org,
linux-arch@...r.kernel.org, Guo Ren <guoren@...ux.alibaba.com>,
Arnd Bergmann <arnd@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
"Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH v2 3/5] csky: Fixup futex SMP implementation
From: Guo Ren <guoren@...ux.alibaba.com>
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@...ux.alibaba.com>
Cc: Arnd Bergmann <arnd@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Paul E. McKenney <paulmck@...nel.org>
Link: https://lore.kernel.org/lkml/CAK8P3a3+WaQNyJ6Za2qfu6=0mBgU1hApnRXrdp1b1=P7wwyRUg@mail.gmail.com/
---
arch/csky/Kconfig | 1 +
arch/csky/include/asm/futex.h | 127 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 128 insertions(+)
create mode 100644 arch/csky/include/asm/futex.h
diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
index 50bb8b4..e254dc2 100644
--- a/arch/csky/Kconfig
+++ b/arch/csky/Kconfig
@@ -49,6 +49,7 @@ 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
index 00000000..dbe2f99
--- /dev/null
+++ b/arch/csky/include/asm/futex.h
@@ -0,0 +1,127 @@
+/* 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" \
+ "4: \n" \
+ " .section .fixup,\"ax\" \n" \
+ " .balign 4 \n" \
+ "5: mov %[r], %[e] \n" \
+ " jmpi 4b \n" \
+ " .previous \n" \
+ " .section __ex_table,\"a\" \n" \
+ " .balign 4 \n" \
+ " .long 1b, 5b \n" \
+ " .long 2b, 5b \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"
+ "4: \n"
+ " .section .fixup,\"ax\" \n"
+ " .balign 4 \n"
+ "5: mov %[r], %[e] \n"
+ " jmpi 4b \n"
+ " .previous \n"
+ " .section __ex_table,\"a\" \n"
+ " .balign 4 \n"
+ " .long 1b, 5b \n"
+ " .long 2b, 5b \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 */
--
2.7.4
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