[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20250810055136.897712-6-tiwei.bie@linux.dev>
Date: Sun, 10 Aug 2025 13:51:31 +0800
From: Tiwei Bie <tiwei.bie@...ux.dev>
To: richard@....at,
anton.ivanov@...bridgegreys.com,
johannes@...solutions.net
Cc: linux-um@...ts.infradead.org,
linux-kernel@...r.kernel.org,
benjamin@...solutions.net,
arnd@...db.de,
tiwei.btw@...group.com,
tiwei.bie@...ux.dev
Subject: [PATCH v2 05/10] um: Determine sleep based on need_resched()
From: Tiwei Bie <tiwei.btw@...group.com>
With SMP and NO_HZ enabled, the CPU may still need to sleep even
if the timer is disarmed. Switch to deciding whether to sleep based
on pending resched. This is a preparation for adding SMP support.
Signed-off-by: Tiwei Bie <tiwei.btw@...group.com>
---
arch/um/include/shared/kern_util.h | 1 +
arch/um/kernel/process.c | 12 ++++++++++--
arch/um/os-Linux/time.c | 11 +++++------
3 files changed, 16 insertions(+), 8 deletions(-)
diff --git a/arch/um/include/shared/kern_util.h b/arch/um/include/shared/kern_util.h
index 00ca3e12fd9a..3daaa5c4b35d 100644
--- a/arch/um/include/shared/kern_util.h
+++ b/arch/um/include/shared/kern_util.h
@@ -55,6 +55,7 @@ extern int __uml_cant_sleep(void);
extern int get_current_pid(void);
extern int copy_from_user_proc(void *to, void *from, int size);
extern char *uml_strdup(const char *string);
+int uml_need_resched(void);
extern unsigned long to_irq_stack(unsigned long *mask_out);
extern unsigned long from_irq_stack(int nested);
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 1be644de9e41..01b935c00454 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -209,10 +209,13 @@ int arch_dup_task_struct(struct task_struct *dst,
void um_idle_sleep(void)
{
- if (time_travel_mode != TT_MODE_OFF)
+ if (time_travel_mode != TT_MODE_OFF) {
time_travel_sleep();
- else
+ } else {
+ raw_local_irq_enable();
os_idle_sleep();
+ raw_local_irq_disable();
+ }
}
void arch_cpu_idle(void)
@@ -225,6 +228,11 @@ int __uml_cant_sleep(void) {
/* Is in_interrupt() really needed? */
}
+int uml_need_resched(void)
+{
+ return need_resched();
+}
+
extern exitcall_t __uml_exitcall_begin, __uml_exitcall_end;
void do_uml_exitcalls(void)
diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c
index 4d5591d96d8c..f25a4196bab7 100644
--- a/arch/um/os-Linux/time.c
+++ b/arch/um/os-Linux/time.c
@@ -98,18 +98,17 @@ long long os_nsecs(void)
*/
void os_idle_sleep(void)
{
- struct itimerspec its;
sigset_t set, old;
- /* block SIGALRM while we analyze the timer state */
+ /* Block SIGALRM while performing the need_resched check. */
sigemptyset(&set);
sigaddset(&set, SIGALRM);
sigprocmask(SIG_BLOCK, &set, &old);
- /* check the timer, and if it'll fire then wait for it */
- timer_gettime(event_high_res_timer, &its);
- if (its.it_value.tv_sec || its.it_value.tv_nsec)
+ /* Sleep if no resched is pending. */
+ if (!uml_need_resched())
sigsuspend(&old);
- /* either way, restore the signal mask */
+
+ /* Restore the signal mask. */
sigprocmask(SIG_UNBLOCK, &set, NULL);
}
--
2.34.1
Powered by blists - more mailing lists