From: Matthias Kruk <m@m10k.eu>
Date: Sat, 8 Aug 2020 10:27:27 +0000 (+0900)
Subject: libc: Add cx_spinlock_t type
X-Git-Url: https://git.corax.cc/?a=commitdiff_plain;h=59e5e9901dc80fdcadd1818efe650495a0efb15d;p=corax

libc: Add cx_spinlock_t type
---

diff --git a/include/corax/spinlock.h b/include/corax/spinlock.h
new file mode 100644
index 0000000..8072d1a
--- /dev/null
+++ b/include/corax/spinlock.h
@@ -0,0 +1,65 @@
+#ifndef __CORAX_SPINLOCK_H
+#define __CORAX_SPINLOCK_H
+
+#include <corax/types.h>
+
+typedef u32_t cx_spinlock_t;
+
+/*
+ * cx_spinlock_lock() - Lock a cx_spinlock, waiting indefinitely
+ *
+ * SYNOPSIS
+ *  void cx_spinlock_lock(cx_spinlock_t *lock);
+ *
+ * DESCRIPTION
+ *  The cx_spinlock_lock() function will indefinitely attempt to lock the cx_spinlock pointed to
+ *  by `lock' until it succeeds, waiting in a busy loop.
+ *
+ * RETURN VALUE
+ *  None
+ *
+ * ERRORS
+ *  This function does not signal any errors.
+ */
+void cx_spinlock_lock(cx_spinlock_t*);
+
+/*
+ * cx_spinlock_trylock() - Attempt to lock a cx_spinlock
+ *
+ * SYNOPSIS
+ *  int cx_spinlock_trylock(cx_spinlock_t *lock);
+ *
+ * DESCRIPTION
+ *  The cx_spinlock_trylock() function will attempt once to lock the spinlock pointed to by
+ *  `lock'. This function will not block.
+ *
+ * RETURN VALUE
+ *  This function returns zero upon success, or a non-zero value if the lock could not be
+ *  acquired.
+ *
+ * ERRORS
+ *  This function does not signal any errors.
+ */
+int cx_spinlock_trylock(cx_spinlock_t*);
+
+/*
+ * cx_spinlock_unlock() - Unlock a cx_spinlock
+ *
+ * SYNOPSIS
+ *  int cx_spinlock_unlock(cx_spinlock_t *lock);
+ *
+ * DESCRIPTION
+ *  The cx_spinlock_unlock() function will unlock the cx_spinlock pointed to by `lock'. This
+ *  function will unlock any cx_spinlock regardless of spinlock ownership, and the spinlock will
+ *  always be unlocked when this function returns.
+ *
+ * RETURN VALUE
+ *  This function returns zero if the lock was not locked, or a non-zero value if the lock had
+ *  been locked. Either way, it is in an unlocked state when the call returns.
+ *
+ * ERRORS
+ *  This function does not signal any errors.
+ */
+int cx_spinlock_unlock(cx_spinlock_t*);
+
+#endif /* __CORAX_SPINLOCK_H */
diff --git a/libc/Makefile b/libc/Makefile
index 074199a..6a80c91 100644
--- a/libc/Makefile
+++ b/libc/Makefile
@@ -1,5 +1,5 @@
 OUTPUT = libc.a
-OBJECTS = syscall.o string.o signal.o start.o stdio.o string_ia32.o unistd.o
+OBJECTS = syscall.o string.o signal.o start.o stdio.o string_ia32.o unistd.o spinlock.o
 PHONY = clean
 INCLUDES = -I../include -I..
 CFLAGS = -m32 -Wall -nostdlib -nodefaultlibs -nostartfiles -ffreestanding $(INCLUDES)
diff --git a/libc/spinlock.S b/libc/spinlock.S
new file mode 100644
index 0000000..66ec7e0
--- /dev/null
+++ b/libc/spinlock.S
@@ -0,0 +1,58 @@
+	.section .text
+
+	.global cx_spinlock_lock
+	.global cx_spinlock_trylock
+	.global cx_spinlock_unlock
+
+#ifdef __i386__
+
+cx_spinlock_lock:
+	movl		4(%esp), %edx
+0:	xorl		%eax, %eax
+	movl		$1, %ecx
+	lock
+	cmpxchgl	%ecx, (%edx)
+	jnz		0b /* lock failed */
+	ret		/* lock succeeded */
+
+cx_spinlock_trylock:
+	movl		4(%esp), %edx
+	xorl		%eax, %eax
+	movl		$1, %ecx
+	lock
+	cmpxchgl	%ecx, (%edx)
+	ret
+
+cx_spinlock_unlock:
+	movl		4(%esp), %edx
+	xorl		%eax, %eax
+	lock
+	xchgl		%eax, (%edx)
+	ret
+
+#endif /* __i386__ */
+
+#ifdef __amd64__
+
+cx_spinlock_lock:
+	xorq		%rax, %rax
+	movl		$1, %ecx
+	lock
+	cmpxchgl	%ecx, (%rdi)
+	jnz		cx_spinlock_lock
+	ret
+
+cx_spinlock_trylock:
+	xorl		%rax, %rax
+	movl		$1, %ecx
+	lock
+	cmpxchgl	%ecx, (%rdi)
+	ret
+
+cx_spinlock_unlock:
+	xorq		%rax, %rax
+	lock
+	xchgl		%eax, (%rdi)
+	ret
+
+#endif /* __amd64__ */