1999-01-31 00:14:01

by Andrea Arcangeli

Subject: Re: [patch] down_norecurse(), down_interruptible_norecurse(), up_norecurse()

On Sat, 30 Jan 1999, Tim Waugh wrote:

> MUTEX_NORECURSE probably isn't for a mutex -- it's semaphores that don't
> want recursion. It would be nicer to have something like
> SEMAPHORE(initval). If I thought long enough about it, I'm fairly sure I
> could come up with a situation where you'd want to initialise a semaphore
> to >1.

Ok. I think the MUTEX word was to tell that you wanted a semaphore
initialized to 1 (as a mutex unlocked), but agreed, SEMAPHORE(x) looks a
better name for the norecursive semaphore initializer.

Andrea Arcangeli

1999-01-31 02:46:26

by Andrea Arcangeli

Subject: Re: [patch] down_norecurse(), down_interruptible_norecurse(), up_norecurse()

On Sun, 31 Jan 1999, Andrea Arcangeli wrote:

> initialized to 1 (as a mutex unlocked), but agreed, SEMAPHORE(x) looks a
> better name for the norecursive semaphore initializer.

Does this looks better to you?

Index: include/asm-i386/semaphore.h
===================================================================
RCS file: /var/cvs/linux/include/asm-i386/semaphore.h,v
retrieving revision 1.1.1.2
diff -u -r1.1.1.2 semaphore.h
--- semaphore.h 1999/01/18 13:39:43 1.1.1.2
+++ linux/include/asm-i386/semaphore.h 1999/01/31 02:03:27
@@ -47,11 +47,17 @@
* Other (saner) architectures would use "wmb()" and "rmb()" to
* do this in a more obvious manner.
*/
-struct semaphore {
- atomic_t count;
- unsigned long owner, owner_depth;
- int waking;
+#define STRUCT_SEMAPHORE \
+ atomic_t count; \
+ unsigned long owner, owner_depth; \
+ int waking; \
struct wait_queue * wait;
+
+struct semaphore {
+ STRUCT_SEMAPHORE
+};
+struct semaphore_norecurse {
+ STRUCT_SEMAPHORE
};

/*
@@ -62,10 +68,11 @@
* operation into the slow path.
*/
#define semaphore_owner(sem) \
- ((struct task_struct *)((2*PAGE_MASK) & (sem)->owner))
+ ((struct task_struct *)(((PAGE_SIZE<<1)-1) & (sem)->owner))

#define MUTEX ((struct semaphore) { ATOMIC_INIT(1), 0, 0, 0, NULL })
#define MUTEX_LOCKED ((struct semaphore) { ATOMIC_INIT(0), 0, 1, 0, NULL })
+#define SEMAPHORE_NORECURSE(val) ((struct semaphore_norecurse) { ATOMIC_INIT(val), 0, 0, 0, NULL })

asmlinkage void __down_failed(void /* special register calling convention */);
asmlinkage int __down_failed_interruptible(void /* params in registers */);
@@ -211,6 +218,69 @@
__asm__ __volatile__(
"# atomic up operation\n\t"
"decl 8(%0)\n\t"
+#ifdef __SMP__
+ "lock ; "
+#endif
+ "incl 0(%0)\n\t"
+ "jle 2f\n"
+ "1:\n"
+ ".section .text.lock,\"ax\"\n"
+ "2:\tpushl $1b\n\t"
+ "jmp __up_wakeup\n"
+ ".previous"
+ :/* no outputs */
+ :"c" (sem)
+ :"memory");
+}
+
+extern inline void down_norecurse(struct semaphore_norecurse * sem)
+{
+ __asm__ __volatile__(
+ "# atomic down operation\n\t"
+#ifdef __SMP__
+ "lock ; "
+#endif
+ "decl 0(%0)\n\t"
+ "js 2f\n\t"
+ "1:\n"
+ ".section .text.lock,\"ax\"\n"
+ "2:\tpushl $1b\n\t"
+ "jmp __down_failed\n"
+ ".previous"
+ :/* no outputs */
+ :"c" (sem)
+ :"memory");
+}
+
+extern inline int down_interruptible_norecurse(struct semaphore_norecurse * sem)
+{
+ int result;
+
+ __asm__ __volatile__(
+ "# atomic interruptible down operation\n\t"
+#ifdef __SMP__
+ "lock ; "
+#endif
+ "decl 0(%1)\n\t"
+ "js 2f\n\t"
+ "xorl %0,%0\n"
+ "1:\n"
+ ".section .text.lock,\"ax\"\n"
+ "2:\tpushl $1b\n\t"
+ "jmp __down_failed_interruptible\n"
+ ".previous"
+ :"=a" (result)
+ :"c" (sem)
+ :"memory");
+ return result;
+}
+
+extern inline void up_norecurse(struct semaphore_norecurse * sem)
+{
+ __asm__ __volatile__(
+ "movl $0,4(%0)\n\t"
+ "movl $-1,8(%0)\n\t"
+ "# atomic up operation\n\t"
#ifdef __SMP__
"lock ; "
#endif


Andrea Arcangeli