Fix RV32 atomic.

- Fix __atomic_compare_exchange_4().
- Add patch for core::sync::atomic.
- Revert kernel Mutex.

kernel/Makefile

@@ -137,6 +137,9 @@ kernel:
 ifeq ($(arch), x86_64)
 	@bootimage build $(build_args)
 else
+	@-patch -p0 -N -b \
+		$(shell rustc --print sysroot)/lib/rustlib/src/rust/src/libcore/sync/atomic.rs \
+		src/arch/riscv32/atomic.patch
 	@CC=$(cc) cargo xbuild $(build_args)
 endif
 

kernel/src/arch/riscv32/atomic.patch

@@ -0,0 +1,57 @@
+--- atomic_backup.rs	2018-10-06 19:59:14.000000000 +0800
++++ atomic.rs	2018-10-26 14:34:31.000000000 +0800
+@@ -125,6 +125,9 @@
+ #[cfg(target_has_atomic = "8")]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub struct AtomicBool {
++    #[cfg(any(target_arch = "riscv32", target_arch = "riscv64"))]
++    v: UnsafeCell<u32>,
++    #[cfg(not(any(target_arch = "riscv32", target_arch = "riscv64")))]
+     v: UnsafeCell<u8>,
+ }
+ 
+@@ -265,6 +268,44 @@
+ pub const ATOMIC_BOOL_INIT: AtomicBool = AtomicBool::new(false);
+ 
+ #[cfg(target_has_atomic = "8")]
++#[cfg(any(target_arch = "riscv32", target_arch = "riscv64"))]
++impl AtomicBool {
++    ///
++    #[inline]
++    #[stable(feature = "rust1", since = "1.0.0")]
++    pub const fn new(v: bool) -> AtomicBool {
++        AtomicBool { v: UnsafeCell::new(v as u32) }
++    }
++
++    ///
++    #[inline]
++    #[stable(feature = "rust1", since = "1.0.0")]
++    pub fn load(&self, order: Ordering) -> bool {
++        unsafe { atomic_load(self.v.get(), order) != 0 }
++    }
++
++    ///
++    #[inline]
++    #[stable(feature = "rust1", since = "1.0.0")]
++    pub fn store(&self, val: bool, order: Ordering) {
++        unsafe { atomic_store(self.v.get(), val as u32, order); }
++    }
++
++    ///
++    #[inline]
++    #[stable(feature = "rust1", since = "1.0.0")]
++    #[cfg(target_has_atomic = "cas")]
++    pub fn compare_and_swap(&self, current: bool, new: bool, order: Ordering) -> bool {
++        loop {
++            if let Ok(val) = unsafe { atomic_compare_exchange(self.v.get(), current as u32, new as u32, order, order) } {
++                return val != 0;
++            }
++        }
++    }
++}
++
++#[cfg(target_has_atomic = "8")]
++#[cfg(not(any(target_arch = "riscv32", target_arch = "riscv64")))]
+ impl AtomicBool {
+     /// Creates a new `AtomicBool`.
+     ///

kernel/src/arch/riscv32/compiler_rt.c

@@ -1,50 +1,27 @@
 // http://llvm.org/docs/Atomics.html#libcalls-atomic
 
-char __atomic_load_1(char *src) {
-    char res = 0;
-    __asm__ __volatile__("amoadd.w.rl %0, zero, (%1)" : "=r"(res) : "r"(src) : "memory");
-    return res;
-}
-
-short __atomic_load_2(short *src) {
-    short res = 0;
-    __asm__ __volatile__("amoadd.w.rl %0, zero, (%1)" : "=r"(res) : "r"(src) : "memory");
-    return res;
-}
-
 int __atomic_load_4(int *src) {
     int res = 0;
     __asm__ __volatile__("amoadd.w.rl %0, zero, (%1)" : "=r"(res) : "r"(src) : "memory");
     return res;
 }
 
-char __atomic_store_1(char *dst, char val) {
-    __asm__ __volatile__("amoswap.w.aq zero, %0, (%1)" :: "r"(val), "r"(dst) : "memory");
-}
-
 int __atomic_store_4(int *dst, int val) {
     __asm__ __volatile__("amoswap.w.aq zero, %0, (%1)" :: "r"(val), "r"(dst) : "memory");
 }
 
-char __atomic_compare_exchange_1(char* dst, char* expected, char desired) {
-    char val = 0;
-    __asm__ __volatile__("lr.w %0, (%1)" : "=r"(val) : "r"(dst) : "memory");
-    if (val == *expected) {
-        int sc_ret = 0;
-        __asm__ __volatile__("sc.w %0, %1, (%2)" : "=r"(sc_ret) : "r"(desired), "r"(dst) : "memory");
-        return sc_ret == 0;
-    }
-    return 0;
-}
-
 char __atomic_compare_exchange_4(int* dst, int* expected, int desired) {
-    int val = 0;
+    int val;
+    // val = *dst
     __asm__ __volatile__("lr.w %0, (%1)" : "=r"(val) : "r"(dst) : "memory");
     if (val == *expected) {
-        int sc_ret = 0;
-        __asm__ __volatile__("sc.w %0, %1, (%2)" : "=r"(sc_ret) : "r"(desired), "r"(dst) : "memory");
-        return sc_ret == 0;
+        int result;
+        // Try: *dst = desired. If success, result = 0, otherwise result != 0.
+        __asm__ __volatile__("sc.w %0, %1, (%2)" : "=r"(result) : "r"(desired), "r"(dst) : "memory");
+        return result == 0;
     }
+    // *expected should always equal to the previous value of *dst
+    *expected = val;
     return 0;
 }
 

kernel/src/arch/x86_64/driver/vga.rs

@@ -1,7 +1,7 @@
 use consts::KERNEL_OFFSET;
 use core::ptr::Unique;
 use core::fmt;
-use sync::SpinLock as Mutex;
+use spin::Mutex;
 use volatile::Volatile;
 use x86_64::instructions::port::Port;
 use logging::Color;

kernel/src/fs.rs

@@ -2,7 +2,7 @@ use simple_filesystem::*;
 use alloc::boxed::Box;
 #[cfg(target_arch = "x86_64")]
 use arch::driver::ide;
-use sync::SpinLock as Mutex;
+use spin::Mutex;
 
 // Hard link user program
 #[cfg(target_arch = "riscv32")]

kernel/src/logging.rs

@@ -1,6 +1,6 @@
 use core::fmt;
 use log::{self, Level, LevelFilter, Log, Metadata, Record};
-use sync::SpinLock as Mutex;
+use spin::Mutex;
 
 lazy_static! {
     static ref log_mutex: Mutex<()> = Mutex::new(());

kernel/src/memory.rs

@@ -1,8 +1,7 @@
 pub use arch::paging::*;
 use bit_allocator::{BitAlloc, BitAlloc4K, BitAlloc64K};
 use consts::MEMORY_OFFSET;
-use sync::{MutexGuard, Spin};
-use sync::SpinLock as Mutex;
+use spin::{Mutex, MutexGuard};
 use super::HEAP_ALLOCATOR;
 use ucore_memory::{*, paging::PageTable};
 use ucore_memory::cow::CowExt;
@@ -49,7 +48,7 @@ lazy_static! {
 }
 
 /// The only way to get active page table
-pub fn active_table() -> MutexGuard<'static, CowExt<ActivePageTable>, Spin> {
+pub fn active_table() -> MutexGuard<'static, CowExt<ActivePageTable>> {
     ACTIVE_TABLE.lock()
 }
 

kernel/src/sync/arch/riscv32/atomic_lock.rs

@@ -1,44 +0,0 @@
-//! RISCV atomic is not currently supported by Rust.
-//! This is a ugly workaround.
-
-use core::cell::UnsafeCell;
-
-extern {
-    fn __atomic_load_4(src: *const u32) -> u32;
-    fn __atomic_store_4(dst: *mut u32, val: u32);
-    fn __atomic_compare_exchange_4(dst: *mut u32, expected: *mut u32, desired: u32) -> bool;
-}
-
-pub struct AtomicLock
-{
-    lock: UnsafeCell<u32>
-}
-
-impl AtomicLock 
-{
-    pub fn new() -> Self {
-        AtomicLock {
-            lock: UnsafeCell::new(0)
-        }
-    }
-
-    /// Returns 1 if lock is acquired
-    pub fn try_lock(&self) -> bool {
-        let mut expected: u32 = 0;
-        unsafe {
-            __atomic_compare_exchange_4(self.lock.get(), &mut expected as *mut u32, 1)
-        }
-    }
-
-    pub fn load(&self) -> bool {
-        unsafe {
-            __atomic_load_4(self.lock.get()) == 1
-        }
-    }
-
-    pub fn store(&self) {
-        unsafe {
-            __atomic_store_4(self.lock.get(), 0);
-        }
-    }
-}

kernel/src/sync/arch/x86_64/atomic_lock.rs

@@ -1,31 +0,0 @@
-use core::sync::atomic::{AtomicBool, Ordering};
-
-pub struct AtomicLock
-{
-    lock: AtomicBool
-}
-
-impl AtomicLock 
-{
-    pub fn new() -> AtomicLock {
-        AtomicLock {
-            lock: AtomicBool::new(false)
-        }
-    }
-
-    pub fn try_lock(&self) -> bool {
-        self.lock.compare_and_swap(false, true, Ordering::Acquire) == false
-    }
-
-    pub fn load(&self) -> bool {
-        self.lock.load(Ordering::Relaxed)
-    }
-
-    pub fn store(&self) {
-        self.lock.store(false, Ordering::Release);
-    }
-}
-
-pub const ATOMIC_LOCK_INIT: AtomicLock = AtomicLock {
-    lock: AtomicBool::new(false)
-};

kernel/src/sync/mod.rs

@@ -53,15 +53,6 @@ pub use self::condvar::*;
 pub use self::mutex::*;
 pub use self::semaphore::*;
 
-#[allow(dead_code)]
-#[cfg(target_arch = "x86_64")]
-#[path = "arch/x86_64/atomic_lock.rs"]
-pub mod atomic_lock;
-
-#[cfg(target_arch = "riscv32")]
-#[path = "arch/riscv32/atomic_lock.rs"]
-pub mod atomic_lock;
-
 mod mutex;
 mod condvar;
 mod semaphore;

kernel/src/sync/mutex.rs

@@ -30,8 +30,8 @@ use arch::interrupt;
 use core::cell::UnsafeCell;
 use core::fmt;
 use core::ops::{Deref, DerefMut};
+use core::sync::atomic::{ATOMIC_BOOL_INIT, AtomicBool, Ordering};
 use super::Condvar;
-use super::atomic_lock::AtomicLock;
 
 pub type SpinLock<T> = Mutex<T, Spin>;
 pub type SpinNoIrqLock<T> = Mutex<T, SpinNoIrq>;
@@ -39,7 +39,7 @@ pub type ThreadLock<T> = Mutex<T, Condvar>;
 
 pub struct Mutex<T: ?Sized, S: MutexSupport>
 {
-    lock: AtomicLock,
+    lock: AtomicBool,
     support: S,
     data: UnsafeCell<T>,
 }
@@ -78,7 +78,7 @@ impl<T, S: MutexSupport> Mutex<T, S>
     /// ```
     pub fn new(user_data: T) -> Mutex<T, S> {
         Mutex {
-            lock: AtomicLock::new(),
+            lock: ATOMIC_BOOL_INIT,
             data: UnsafeCell::new(user_data),
             support: S::new(),
         }
@@ -96,9 +96,9 @@ impl<T, S: MutexSupport> Mutex<T, S>
 impl<T: ?Sized, S: MutexSupport> Mutex<T, S>
 {
     fn obtain_lock(&self) {
-        while !self.lock.try_lock() {
+        while self.lock.compare_and_swap(false, true, Ordering::Acquire) != false {
             // Wait until the lock looks unlocked before retrying
-            while self.lock.load() {
+            while self.lock.load(Ordering::Relaxed) {
                 self.support.cpu_relax();
             }
         }
@@ -137,14 +137,14 @@ impl<T: ?Sized, S: MutexSupport> Mutex<T, S>
     ///
     /// If the lock isn't held, this is a no-op.
     pub unsafe fn force_unlock(&self) {
-        self.lock.store();
+        self.lock.store(false, Ordering::Release);
     }
 
     /// Tries to lock the mutex. If it is already locked, it will return None. Otherwise it returns
     /// a guard within Some.
     pub fn try_lock(&self) -> Option<MutexGuard<T, S>> {
         let support_guard = S::before_lock();
-        if self.lock.try_lock() {
+        if self.lock.compare_and_swap(false, true, Ordering::Acquire) == false {
             Some(MutexGuard {
                 mutex: self,
                 support_guard,
@@ -174,19 +174,19 @@ impl<T: ?Sized + Default, S: MutexSupport> Default for Mutex<T, S> {
 impl<'a, T: ?Sized, S: MutexSupport> Deref for MutexGuard<'a, T, S>
 {
     type Target = T;
-    fn deref<'b>(&'b self) -> &'b T { unsafe { &*self.mutex.data.get() } }
+    fn deref(&self) -> &T { unsafe { &*self.mutex.data.get() } }
 }
 
 impl<'a, T: ?Sized, S: MutexSupport> DerefMut for MutexGuard<'a, T, S>
 {
-    fn deref_mut<'b>(&'b mut self) -> &'b mut T { unsafe { &mut *self.mutex.data.get() } }
+    fn deref_mut(&mut self) -> &mut T { unsafe { &mut *self.mutex.data.get() } }
 }
 
 impl<'a, T: ?Sized, S: MutexSupport> Drop for MutexGuard<'a, T, S>
 {
     /// The dropping of the MutexGuard will release the lock it was created from.
     fn drop(&mut self) {
-        self.mutex.lock.store();
+        self.mutex.lock.store(false, Ordering::Release);
         self.mutex.support.after_unlock();
     }
 }