[SeaBIOS] [PATCH] Some improvements to optionrom preemption support.
Kevin O'Connor
kevin at koconnor.net
Sat Apr 3 02:15:58 CEST 2010
Enable preemption during VGA mode switch call - this call can take
several milliseconds on real hardware.
Call yield() in finish_preempt() - when preemption is configured it
allows threads in wait_preempt() to run; when not configured it gives
an opportunity for threads to execute after the implicit delay from
optionrom execution.
Don't penalize priority in run_thread(). The run_thread() code would
implicitly yield because it created the new thread on the list after
the current thread and then jumped to it. When in a preemption event,
a yield effectively waits approximately one millisecond (to the next
rtc irq). The implicit yielding in run_thread thus limited the number
of threads one could launch during preemption to 1 per millisecond.
So, change the code so that the new thread is created prior to the
current thread - thus eliminating the effective yield from
run_thread().
---
src/optionroms.c | 2 ++
src/stacks.c | 21 ++++++++++++++-------
2 files changed, 16 insertions(+), 7 deletions(-)
diff --git a/src/optionroms.c b/src/optionroms.c
index 47f5808..ad88e0c 100644
--- a/src/optionroms.c
+++ b/src/optionroms.c
@@ -470,7 +470,9 @@ vga_setup(void)
memset(&br, 0, sizeof(br));
br.flags = F_IF;
br.ax = 0x0003;
+ start_preempt();
call16_int(0x10, &br);
+ finish_preempt();
// Write to screen.
printf("Starting SeaBIOS (version %s)\n\n", VERSION);
diff --git a/src/stacks.c b/src/stacks.c
index 570948a..92d91a0 100644
--- a/src/stacks.c
+++ b/src/stacks.c
@@ -116,9 +116,12 @@ stack_hop(u32 eax, u32 edx, void *func)
#define THREADSTACKSIZE 4096
+// Thread info - stored at bottom of each thread stack - don't change
+// without also updating the inline assembler below.
struct thread_info {
struct thread_info *next;
void *stackpos;
+ struct thread_info **pprev;
};
struct thread_info VAR16VISIBLE MainThread;
@@ -128,6 +131,7 @@ void
thread_setup(void)
{
MainThread.next = &MainThread;
+ MainThread.pprev = &MainThread.next;
MainThread.stackpos = NULL;
CanPreempt = 0;
}
@@ -185,10 +189,8 @@ yield(void)
static void
__end_thread(struct thread_info *old)
{
- struct thread_info *pos = &MainThread;
- while (pos->next != old)
- pos = pos->next;
- pos->next = old->next;
+ old->next->pprev = old->pprev;
+ *old->pprev = old->next;
free(old);
dprintf(DEBUG_thread, "\\%08x/ End thread\n", (u32)old);
}
@@ -207,8 +209,10 @@ run_thread(void (*func)(void*), void *data)
thread->stackpos = (void*)thread + THREADSTACKSIZE;
struct thread_info *cur = getCurThread();
- thread->next = cur->next;
- cur->next = thread;
+ thread->next = cur;
+ thread->pprev = cur->pprev;
+ cur->pprev = &thread->next;
+ *thread->pprev = thread;
dprintf(DEBUG_thread, "/%08x\\ Start thread\n", (u32)thread);
asm volatile(
@@ -289,11 +293,14 @@ start_preempt(void)
void
finish_preempt(void)
{
- if (! CONFIG_THREADS || ! CONFIG_THREAD_OPTIONROMS)
+ if (! CONFIG_THREADS || ! CONFIG_THREAD_OPTIONROMS) {
+ yield();
return;
+ }
CanPreempt = 0;
releaseRTC();
dprintf(1, "Done preempt - %d checks\n", PreemptCount);
+ yield();
}
// Check if preemption is on, and wait for it to complete if so.
--
1.6.6.1
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