Fixed priority inheritance issues with PI semaphores. Added regular

semaphores accessible through system calls, so that they can be used with
the LSO (for partitioned FMLP).

4 files changed, 86 insertions, 6 deletions

diff --git a/arch/i386/kernel/Makefile b/arch/i386/kernel/Makefile
index 46cf523b44..b8815ad4e8 100644
--- a/arch/i386/kernel/Makefile
+++ b/arch/i386/kernel/Makefile
@@ -8,7 +8,7 @@ obj-y	:= process.o signal.o entry.o traps.o irq.o \
                 ptrace.o time.o ioport.o ldt.o setup.o i8259.o sys_i386.o \
                 pci-dma.o i386_ksyms.o i387.o bootflag.o e820.o\
                 quirks.o i8237.o topology.o alternative.o i8253.o tsc.o \
-                pi_sem_syscalls.o
+                pi_sem_syscalls.o sem_syscalls.o
 
 obj-$(CONFIG_STACKTRACE)        += stacktrace.o
 obj-y                           += cpu/
diff --git a/arch/i386/kernel/pi_sem_syscalls.c b/arch/i386/kernel/pi_sem_syscalls.c
index 06317c7145..f7a66da110 100644
--- a/arch/i386/kernel/pi_sem_syscalls.c
+++ b/arch/i386/kernel/pi_sem_syscalls.c
@@ -1,5 +1,3 @@
-#include <linux/linkage.h>
-
 #ifdef __KERNEL__
 
 /*
@@ -40,7 +38,7 @@ asmlinkage long sys_pi_sema_init (void)
                         atomic_set(&pi_sems[sem_id].count, 1);
                         pi_sems[sem_id].sleepers = 0;
                         init_waitqueue_head(&pi_sems[sem_id].wait);
-                        pi_sems[sem_id].sem_prio = LOWEST_SEM_PRIO;
+                        pi_sems[sem_id].sem_hp_task = NULL;
                         return sem_id;
                 }
         }
diff --git a/arch/i386/kernel/sem_syscalls.c b/arch/i386/kernel/sem_syscalls.c
new file mode 100644
index 0000000000..2bdbc5fd96
--- /dev/null
+++ b/arch/i386/kernel/sem_syscalls.c
@@ -0,0 +1,78 @@
+/*
+ * SMP- and interrupt-safe semaphores, using system calls from user space,
+ * so that they work with the LSO. Uses semaphores as described in
+ * include/asm-i386/semaphore.h.
+ */
+
+#include <asm/semaphore.h>
+#include <linux/sched.h>
+
+#define MAX_SEMAPHORES 256
+
+struct semaphore sems[MAX_SEMAPHORES]; /* all sems */
+typedef int sema_id; /* Userspace ID of a semaphore */
+
+/* Initialize semaphores at boot time. */
+static int __init sema_boot_init(void)
+{        
+        sema_id sem_id;
+
+        printk("Initializing semaphores...");
+        for (sem_id = 0; sem_id < MAX_SEMAPHORES; sem_id++)
+                sems[sem_id].used = 0;
+        printk(" complete!\n");
+
+        return 0;
+}
+__initcall(sema_boot_init);
+
+/* Find a free semaphore and assign to sem. */
+asmlinkage long sys_sema_init (void)
+{
+        sema_id sem_id;
+
+        for (sem_id = 0; sem_id < MAX_SEMAPHORES; sem_id++) {                                 
+                if (!cmpxchg(&sems[sem_id].used, 0, 1)) {                                                        
+                        sema_init(&sems[sem_id], 1);
+                        return sem_id;
+                }
+        }
+        return -ENOMEM;
+}
+
+asmlinkage long sys_down(sema_id sem_id)
+{
+        if (sem_id < 0 || sem_id >= MAX_SEMAPHORES)
+                return -EINVAL;
+
+        down(&sems[sem_id]);
+        return 0;
+}
+
+asmlinkage long sys_up(sema_id sem_id)
+{        
+        if (sem_id < 0 || sem_id >= MAX_SEMAPHORES)
+                return -EINVAL;
+
+        up(&sems[sem_id]);
+        return 0;
+}
+
+asmlinkage long sys_sema_free(sema_id sem_id)
+{
+        struct list_head *tmp, *next;
+        unsigned long flags;
+
+        spin_lock_irqsave(&sems[sem_id].wait.lock, flags);
+        list_for_each_safe(tmp, next, &sems[sem_id].wait.task_list) {
+                wait_queue_t *curr = list_entry(tmp, wait_queue_t, task_list);
+                list_del(tmp);
+                curr->func(curr, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
+                           0, NULL);
+        }
+        spin_unlock_irqrestore(&sems[sem_id].wait.lock, flags);
+        sems[sem_id].used = 0;
+
+        return 0;
+}
+
diff --git a/arch/i386/kernel/syscall_table.S b/arch/i386/kernel/syscall_table.S
index 297a511c37..10e0ce444d 100644
--- a/arch/i386/kernel/syscall_table.S
+++ b/arch/i386/kernel/syscall_table.S
@@ -335,5 +335,9 @@ ENTRY(sys_call_table)
         .long sys_pi_down
         .long sys_pi_up                 
         .long sys_pi_sema_free
-        .long sys_in_blocking_zone      /* 335 */
-        .long sys_wait_for_zone_exit    /* 336 */
+        .long sys_sema_init             /* 335 */
+        .long sys_down
+        .long sys_up
+        .long sys_sema_free
+        .long sys_in_blocking_zone
+        .long sys_wait_for_zone_exit    /* 340 */