* Context switching is only done cooperatively.
*
* \version $Id$
- *
* \author Bernie Innocenti <bernie@codewiz.org>
* \author Stefano Fedrigo <aleph@develer.com>
*/
-
#include "proc_p.h"
#include "proc.h"
#include "cfg/cfg_arch.h" /* ARCH_EMUL */
#include <cfg/debug.h>
#include <cfg/module.h>
-#include <cfg/macros.h> /* ABS() */
+
+// Log settings for cfg/log.h.
+#define LOG_LEVEL KERN_LOG_LEVEL
+#define LOG_FORMAT KERN_LOG_FORMAT
+#include <cfg/log.h>
#include <cpu/irq.h>
#include <cpu/types.h>
/**
* CPU dependent context switching routines.
*
- * \note This function *MUST* preserve also the status of the interrupts.
+ * Saving and restoring the context on the stack is done by a CPU-dependent
+ * support routine which usually needs to be written in assembly.
*/
EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
/*
- * The scheduer tracks ready and waiting processes
- * by enqueuing them in these lists. A pointer to the currently
- * running process is stored in the CurrentProcess pointer.
+ * The scheduer tracks ready processes by enqueuing them in the
+ * ready list.
*
- * NOTE: these variables are protected by DI/EI locking
+ * \note Access to the list must occur while interrupts are disabled.
*/
-REGISTER Process *CurrentProcess;
-REGISTER List ProcReadyList;
+REGISTER List ProcReadyList;
+/*
+ * Holds a pointer to the TCB of the currently running process.
+ *
+ * \note User applications should use proc_current() to retrieve this value.
+ */
+REGISTER Process *CurrentProcess;
#if CONFIG_KERN_PREEMPTIVE
/*
- * The time sharing scheduler forces a task switch when
- * the current process has consumed its quantum.
+ * The time sharing scheduler forces a task switch when the current
+ * process has exhausted its quantum.
*/
uint16_t Quantum;
#endif
-/* In Win32 we must emulate stack on the real process stack */
#if (ARCH & ARCH_EMUL)
+/*
+ * In hosted environments, we must emulate the stack on the real process stack.
+ *
+ * Access to this list must be protected by PROC_ATOMIC().
+ */
extern List StackFreeList;
#endif
{
LIST_INIT(&ProcReadyList);
-#if CONFIG_KERN_MONITOR
- monitor_init();
-#endif
-
- /* We "promote" the current context into a real process. The only thing we have
+ /*
+ * We "promote" the current context into a real process. The only thing we have
* to do is create a PCB and make it current. We don't need to setup the stack
* pointer because it will be written the first time we switch to another process.
*/
proc_init_struct(&MainProcess);
CurrentProcess = &MainProcess;
+#if CONFIG_KERN_MONITOR
+ monitor_init();
+ monitor_add(CurrentProcess, "main");
+#endif
+
MOD_INIT(proc);
}
#if CONFIG_KERN_HEAP
bool free_stack = false;
#endif
+ TRACEMSG("name=%s", name);
#if (ARCH & ARCH_EMUL)
/* Ignore stack provided by caller and use the large enough default instead. */
- stack_base = (cpustack_t *)list_remHead(&StackFreeList);
+ PROC_ATOMIC(stack_base = (cpustack_t *)list_remHead(&StackFreeList));
stack_size = CONFIG_PROC_DEFSTACKSIZE;
#elif CONFIG_KERN_HEAP
}
#else
/* Stack must have been provided by the user */
- ASSERT(stack_base);
+ ASSERT_VALID_PTR(stack_base);
ASSERT(stack_size);
#endif
#if CONFIG_KERN_MONITOR
/* Fill-in the stack with a special marker to help debugging */
+#warning size incorrect
memset(stack_base, CONFIG_KERN_STACKFILLCODE, stack_size / sizeof(cpustack_t));
#endif
/* Add to ready list */
ATOMIC(SCHED_ENQUEUE(proc));
+ ATOMIC(LIST_ASSERT_VALID(&ProcReadyList));
#if CONFIG_KERN_MONITOR
monitor_add(proc, name);
/**
* System scheduler: pass CPU control to the next process in
* the ready queue.
- *
- * Saving and restoring the context on the stack is done
- * by a CPU-dependent support routine which must usually be
- * written in assembly.
*/
void proc_schedule(void)
{
struct Process *old_process;
cpuflags_t flags;
+ ATOMIC(LIST_ASSERT_VALID(&ProcReadyList));
+ ASSERT_USER_CONTEXT();
+ ASSERT_IRQ_ENABLED();
+
/* Remember old process to save its context later */
old_process = CurrentProcess;
-#ifdef IRQ_RUNNING
- /* Scheduling in interrupts is a nono. */
- ASSERT(!IRQ_RUNNING());
-#endif
-
/* Poll on the ready queue for the first ready process */
IRQ_SAVE_DISABLE(flags);
while (!(CurrentProcess = (struct Process *)list_remHead(&ProcReadyList)))
{
cpustack_t *dummy;
-#if CONFIG_KERN_PREEMPTIVE
- /* Reset quantum for this process */
- Quantum = CONFIG_KERN_QUANTUM;
-#endif
+ #if CONFIG_KERN_MONITOR
+ LOG_INFO("Switch from %p(%s) to %p(%s)\n",
+ old_process, old_process ? old_process->monitor.name : "NONE",
+ CurrentProcess, CurrentProcess->monitor.name);
+ #endif
+
+ #if CONFIG_KERN_PREEMPTIVE
+ /* Reset quantum for this process */
+ Quantum = CONFIG_KERN_QUANTUM;
+ #endif
/* Save context of old process and switch to new process. If there is no
* old process, we save the old stack pointer into a dummy variable that
*/
void proc_exit(void)
{
+ TRACE;
+
#if CONFIG_KERN_MONITOR
monitor_remove(CurrentProcess);
#endif
#if (ARCH & ARCH_EMUL)
#warning This is wrong
/* Reinsert process stack in free list */
- ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
- - (CONFIG_PROC_DEFSTACKSIZE / sizeof(cpustack_t))));
+ PROC_ATOMIC(ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
+ - (CONFIG_PROC_DEFSTACKSIZE / sizeof(cpustack_t)))));
/*
* NOTE: At this point the first two words of what used
*/
void proc_switch(void)
{
- cpuflags_t flags;
-
- IRQ_SAVE_DISABLE(flags);
- SCHED_ENQUEUE(CurrentProcess);
- IRQ_RESTORE(flags);
+ ATOMIC(SCHED_ENQUEUE(CurrentProcess));
proc_schedule();
}
* invalidate any other reasons why the executable file might be covered by
* the GNU General Public License.
*
- * Copyright 2004 Develer S.r.l. (http://www.develer.com/)
+ * Copyright 2004, 2008 Develer S.r.l. (http://www.develer.com/)
* Copyright 1999, 2000, 2001 Bernie Innocenti <bernie@codewiz.org>
*
* -->
sigmask_t result;
cpuflags_t flags;
+ /*
+ * This is subtle: there's a race condition where a concurrent
+ * process or an interrupt calls sig_signal() to set a bit in
+ * out sig_recv just after we have checked for it, but before
+ * we've set sig_wait to tell them we want to be awaken.
+ *
+ * In this case, we'd deadlock with the signal bit already
+ * set and the process never being reinserted into the ready
+ * list.
+ */
IRQ_SAVE_DISABLE(flags);
/* Loop until we get at least one of the signals */
while (!(result = CurrentProcess->sig_recv & sigs))
{
- /* go to sleep and proc_schedule() another process */
+ /*
+ * Tell "them" that we want to be awaken when any of these
+ * signals arrives.
+ */
CurrentProcess->sig_wait = sigs;
- proc_schedule();
- /* When we come back here, a signal must be arrived */
+ /*
+ * Go to sleep and proc_schedule() another process.
+ *
+ * We re-enable IRQs because proc_schedule() does not
+ * guarantee to save and restore the interrupt mask.
+ */
+ IRQ_RESTORE(flags);
+ proc_schedule();
+ IRQ_SAVE_DISABLE(flags);
+
+ /*
+ * When we come back here, the wait mask must have been
+ * cleared by someone through sig_signal(), and at least
+ * one of the signals we were expecting must have been
+ * delivered to us.
+ */
ASSERT(!CurrentProcess->sig_wait);
- ASSERT(CurrentProcess->sig_recv);
+ ASSERT(CurrentProcess->sig_recv & sigs);
}
/* Signals found: clear them and return */
void sig_signal(Process *proc, sigmask_t sigs)
{
cpuflags_t flags;
+
+ /* See comment in sig_wait() for why this protection is necessary */
IRQ_SAVE_DISABLE(flags);
/* Set the signals */
}
#endif /* CONFIG_KERN_SIGNALS */
-
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