| Message ID | 20220831175920.2806-5-jszhang@kernel.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | riscv: add PREEMPT_RT support | expand |
On Thu, Sep 1, 2022 at 2:08 AM Jisheng Zhang <jszhang@kernel.org> wrote: > > Implement the lazy preempt for riscv. > > Signed-off-by: Jisheng Zhang <jszhang@kernel.org> > --- > arch/riscv/Kconfig | 1 + > arch/riscv/include/asm/thread_info.h | 7 +++++-- > arch/riscv/kernel/asm-offsets.c | 1 + > arch/riscv/kernel/entry.S | 9 +++++++-- > 4 files changed, 14 insertions(+), 4 deletions(-) > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > index 7a8134fd7ec9..9f2f1936b1b5 100644 > --- a/arch/riscv/Kconfig > +++ b/arch/riscv/Kconfig > @@ -105,6 +105,7 @@ config RISCV > select HAVE_PERF_REGS > select HAVE_PERF_USER_STACK_DUMP > select HAVE_POSIX_CPU_TIMERS_TASK_WORK > + select HAVE_PREEMPT_LAZY > select HAVE_REGS_AND_STACK_ACCESS_API > select HAVE_FUNCTION_ARG_ACCESS_API > select HAVE_STACKPROTECTOR > diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h > index 78933ac04995..471915b179a2 100644 > --- a/arch/riscv/include/asm/thread_info.h > +++ b/arch/riscv/include/asm/thread_info.h > @@ -56,6 +56,7 @@ > struct thread_info { > unsigned long flags; /* low level flags */ > int preempt_count; /* 0=>preemptible, <0=>BUG */ > + int preempt_lazy_count; /* 0=>preemptible, <0=>BUG */ > /* > * These stack pointers are overwritten on every system call or > * exception. SP is also saved to the stack it can be recovered when > @@ -90,7 +91,7 @@ struct thread_info { > #define TIF_NOTIFY_RESUME 1 /* callback before returning to user */ > #define TIF_SIGPENDING 2 /* signal pending */ > #define TIF_NEED_RESCHED 3 /* rescheduling necessary */ > -#define TIF_RESTORE_SIGMASK 4 /* restore signal mask in do_signal() */ > +#define TIF_NEED_RESCHED_LAZY 4 /* lazy rescheduling */ > #define TIF_MEMDIE 5 /* is terminating due to OOM killer */ > #define TIF_SYSCALL_TRACEPOINT 6 /* syscall tracepoint instrumentation */ > #define TIF_SYSCALL_AUDIT 7 /* syscall auditing */ > @@ -98,6 +99,7 @@ struct thread_info { > #define TIF_NOTIFY_SIGNAL 9 /* signal notifications exist */ > #define TIF_UPROBE 10 /* uprobe breakpoint or singlestep */ > #define TIF_32BIT 11 /* compat-mode 32bit process */ > +#define TIF_RESTORE_SIGMASK 12 /* restore signal mask in do_signal() */ > > #define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE) > #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME) > @@ -108,10 +110,11 @@ struct thread_info { > #define _TIF_SECCOMP (1 << TIF_SECCOMP) > #define _TIF_NOTIFY_SIGNAL (1 << TIF_NOTIFY_SIGNAL) > #define _TIF_UPROBE (1 << TIF_UPROBE) > +#define _TIF_NEED_RESCHED_LAZY (1 << TIF_NEED_RESCHED_LAZY) > > #define _TIF_WORK_MASK \ > (_TIF_NOTIFY_RESUME | _TIF_SIGPENDING | _TIF_NEED_RESCHED | \ > - _TIF_NOTIFY_SIGNAL | _TIF_UPROBE) > + _TIF_NEED_RESCHED_LAZY | _TIF_NOTIFY_SIGNAL | _TIF_UPROBE) > > #define _TIF_SYSCALL_WORK \ > (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_AUDIT | \ > diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c > index df9444397908..e38e33822f72 100644 > --- a/arch/riscv/kernel/asm-offsets.c > +++ b/arch/riscv/kernel/asm-offsets.c > @@ -35,6 +35,7 @@ void asm_offsets(void) > OFFSET(TASK_THREAD_S11, task_struct, thread.s[11]); > OFFSET(TASK_TI_FLAGS, task_struct, thread_info.flags); > OFFSET(TASK_TI_PREEMPT_COUNT, task_struct, thread_info.preempt_count); > + OFFSET(TASK_TI_PREEMPT_LAZY_COUNT, task_struct, thread_info.preempt_lazy_count); > OFFSET(TASK_TI_KERNEL_SP, task_struct, thread_info.kernel_sp); > OFFSET(TASK_TI_USER_SP, task_struct, thread_info.user_sp); > > diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S > index b9eda3fcbd6d..595100a4c2c7 100644 > --- a/arch/riscv/kernel/entry.S > +++ b/arch/riscv/kernel/entry.S > @@ -361,9 +361,14 @@ restore_all: > resume_kernel: > REG_L s0, TASK_TI_PREEMPT_COUNT(tp) > bnez s0, restore_all > - REG_L s0, TASK_TI_FLAGS(tp) > - andi s0, s0, _TIF_NEED_RESCHED > + REG_L s1, TASK_TI_FLAGS(tp) > + andi s0, s1, _TIF_NEED_RESCHED > + bnez s0, 1f > + REG_L s0, TASK_TI_PREEMPT_LAZY_COUNT(tp) > + bnez s0, restore_all > + andi s0, s1, _TIF_NEED_RESCHED_LAZY Can you tell me, who increased/decreased the PREEMPT_LAZY_COUNT? And who set NEED_RESCHED_LAZY? > beqz s0, restore_all > +1: > call preempt_schedule_irq > j restore_all > #endif > -- > 2.34.1 > > > -- > kvm-riscv mailing list > kvm-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kvm-riscv
On 2022-09-04 23:16:12 [+0800], Guo Ren wrote: > > diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S > > index b9eda3fcbd6d..595100a4c2c7 100644 > > --- a/arch/riscv/kernel/entry.S > > +++ b/arch/riscv/kernel/entry.S > > @@ -361,9 +361,14 @@ restore_all: > > resume_kernel: > > REG_L s0, TASK_TI_PREEMPT_COUNT(tp) > > bnez s0, restore_all > > - REG_L s0, TASK_TI_FLAGS(tp) > > - andi s0, s0, _TIF_NEED_RESCHED > > + REG_L s1, TASK_TI_FLAGS(tp) > > + andi s0, s1, _TIF_NEED_RESCHED > > + bnez s0, 1f > > + REG_L s0, TASK_TI_PREEMPT_LAZY_COUNT(tp) > > + bnez s0, restore_all > > + andi s0, s1, _TIF_NEED_RESCHED_LAZY > Can you tell me, who increased/decreased the PREEMPT_LAZY_COUNT? And > who set NEED_RESCHED_LAZY? There is "generic" code in the PREEMPT_RT patch doing that. The counter is incremented/ decremented via preempt_lazy_enable()/disable() and one of the user is migrate_disable()/enable(). Basically if a task is task_is_realtime() then NEED_RESCHED is set for the wakeup. For the remaining states (SCHED_OTHER, …) NEED_RESCHED_LAZY is set for the wakeup. This can be delayed if the task is in a "preempt disable lazy" section (similar to a preempt_disable() section) but a task_is_realtime() can still be scheduled if needed. See details at https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/plain/patches/sched__Add_support_for_lazy_preemption.patch?h=linux-6.0.y-rt-patches Sebastian
On Mon, Sep 5, 2022 at 2:34 PM Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote: > > On 2022-09-04 23:16:12 [+0800], Guo Ren wrote: > > > diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S > > > index b9eda3fcbd6d..595100a4c2c7 100644 > > > --- a/arch/riscv/kernel/entry.S > > > +++ b/arch/riscv/kernel/entry.S > > > @@ -361,9 +361,14 @@ restore_all: > > > resume_kernel: > > > REG_L s0, TASK_TI_PREEMPT_COUNT(tp) > > > bnez s0, restore_all > > > - REG_L s0, TASK_TI_FLAGS(tp) > > > - andi s0, s0, _TIF_NEED_RESCHED > > > + REG_L s1, TASK_TI_FLAGS(tp) > > > + andi s0, s1, _TIF_NEED_RESCHED > > > + bnez s0, 1f > > > + REG_L s0, TASK_TI_PREEMPT_LAZY_COUNT(tp) > > > + bnez s0, restore_all > > > + andi s0, s1, _TIF_NEED_RESCHED_LAZY > > Can you tell me, who increased/decreased the PREEMPT_LAZY_COUNT? And > > who set NEED_RESCHED_LAZY? > > There is "generic" code in the PREEMPT_RT patch doing that. The counter > is incremented/ decremented via preempt_lazy_enable()/disable() and one > of the user is migrate_disable()/enable(). > Basically if a task is task_is_realtime() then NEED_RESCHED is set for > the wakeup. For the remaining states (SCHED_OTHER, …) NEED_RESCHED_LAZY > is set for the wakeup. This can be delayed if the task is in a "preempt > disable lazy" section (similar to a preempt_disable() section) but a > task_is_realtime() can still be scheduled if needed. Okay, It should be [PATCH RT]. RISC-V would also move to GENERIC_ENTRY [1], so above assembly code would be replaced by generic one, right? [1]: https://lore.kernel.org/linux-riscv/20220904072637.8619-3-guoren@kernel.org/T/#u > See details at > https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/plain/patches/sched__Add_support_for_lazy_preemption.patch?h=linux-6.0.y-rt-patches > > Sebastian
On 2022-09-05 16:33:54 [+0800], Guo Ren wrote: > > There is "generic" code in the PREEMPT_RT patch doing that. The counter > > is incremented/ decremented via preempt_lazy_enable()/disable() and one > > of the user is migrate_disable()/enable(). > > Basically if a task is task_is_realtime() then NEED_RESCHED is set for > > the wakeup. For the remaining states (SCHED_OTHER, …) NEED_RESCHED_LAZY > > is set for the wakeup. This can be delayed if the task is in a "preempt > > disable lazy" section (similar to a preempt_disable() section) but a > > task_is_realtime() can still be scheduled if needed. > Okay, It should be [PATCH RT]. RISC-V would also move to GENERIC_ENTRY > [1], so above assembly code would be replaced by generic one, right? correct. Sebastian
On Mon, Sep 05, 2022 at 04:33:54PM +0800, Guo Ren wrote: > On Mon, Sep 5, 2022 at 2:34 PM Sebastian Andrzej Siewior > <bigeasy@linutronix.de> wrote: > > > > On 2022-09-04 23:16:12 [+0800], Guo Ren wrote: > > > > diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S > > > > index b9eda3fcbd6d..595100a4c2c7 100644 > > > > --- a/arch/riscv/kernel/entry.S > > > > +++ b/arch/riscv/kernel/entry.S > > > > @@ -361,9 +361,14 @@ restore_all: > > > > resume_kernel: > > > > REG_L s0, TASK_TI_PREEMPT_COUNT(tp) > > > > bnez s0, restore_all > > > > - REG_L s0, TASK_TI_FLAGS(tp) > > > > - andi s0, s0, _TIF_NEED_RESCHED > > > > + REG_L s1, TASK_TI_FLAGS(tp) > > > > + andi s0, s1, _TIF_NEED_RESCHED > > > > + bnez s0, 1f > > > > + REG_L s0, TASK_TI_PREEMPT_LAZY_COUNT(tp) > > > > + bnez s0, restore_all > > > > + andi s0, s1, _TIF_NEED_RESCHED_LAZY > > > Can you tell me, who increased/decreased the PREEMPT_LAZY_COUNT? And > > > who set NEED_RESCHED_LAZY? > > > > There is "generic" code in the PREEMPT_RT patch doing that. The counter > > is incremented/ decremented via preempt_lazy_enable()/disable() and one > > of the user is migrate_disable()/enable(). > > Basically if a task is task_is_realtime() then NEED_RESCHED is set for > > the wakeup. For the remaining states (SCHED_OTHER, …) NEED_RESCHED_LAZY > > is set for the wakeup. This can be delayed if the task is in a "preempt > > disable lazy" section (similar to a preempt_disable() section) but a > > task_is_realtime() can still be scheduled if needed. > Okay, It should be [PATCH RT]. RISC-V would also move to GENERIC_ENTRY As said in the cover letter, this patch is expected to reviewed and maintained in RT tree. If your GENERIC_ENTRY patches are merged, I will send an updated patch. > [1], so above assembly code would be replaced by generic one, right? > > [1]: https://lore.kernel.org/linux-riscv/20220904072637.8619-3-guoren@kernel.org/T/#u > > > > See details at > > https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/plain/patches/sched__Add_support_for_lazy_preemption.patch?h=linux-6.0.y-rt-patches > > > > > > Sebastian > > > > -- > Best Regards > Guo Ren
On Mon, Sep 5, 2022 at 4:46 PM Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote: > > On 2022-09-05 16:33:54 [+0800], Guo Ren wrote: > > > There is "generic" code in the PREEMPT_RT patch doing that. The counter > > > is incremented/ decremented via preempt_lazy_enable()/disable() and one > > > of the user is migrate_disable()/enable(). > > > Basically if a task is task_is_realtime() then NEED_RESCHED is set for > > > the wakeup. For the remaining states (SCHED_OTHER, …) NEED_RESCHED_LAZY > > > is set for the wakeup. This can be delayed if the task is in a "preempt > > > disable lazy" section (similar to a preempt_disable() section) but a > > > task_is_realtime() can still be scheduled if needed. > > Okay, It should be [PATCH RT]. RISC-V would also move to GENERIC_ENTRY > > [1], so above assembly code would be replaced by generic one, right? > > correct. Maybe TIF_XXX_RESCHED also could be merged into GENERIC_ENTRY, just like what you've done in syscall. struct thread_info { unsigned long flags; unsigned long syscall_work; /* SYSCALL_WORK_ flags */ + unsigned long resched_work; /* RESCHED flags */ Or merge them into one: struct thread_info { unsigned long flags; - unsigned long syscall_work; /* SYSCALL_WORK_ flags */ + unsigned long ge_flags; /* GENERIC_ENTRY flags */ > > Sebastian
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 7a8134fd7ec9..9f2f1936b1b5 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -105,6 +105,7 @@ config RISCV select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP select HAVE_POSIX_CPU_TIMERS_TASK_WORK + select HAVE_PREEMPT_LAZY select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_FUNCTION_ARG_ACCESS_API select HAVE_STACKPROTECTOR diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h index 78933ac04995..471915b179a2 100644 --- a/arch/riscv/include/asm/thread_info.h +++ b/arch/riscv/include/asm/thread_info.h @@ -56,6 +56,7 @@ struct thread_info { unsigned long flags; /* low level flags */ int preempt_count; /* 0=>preemptible, <0=>BUG */ + int preempt_lazy_count; /* 0=>preemptible, <0=>BUG */ /* * These stack pointers are overwritten on every system call or * exception. SP is also saved to the stack it can be recovered when @@ -90,7 +91,7 @@ struct thread_info { #define TIF_NOTIFY_RESUME 1 /* callback before returning to user */ #define TIF_SIGPENDING 2 /* signal pending */ #define TIF_NEED_RESCHED 3 /* rescheduling necessary */ -#define TIF_RESTORE_SIGMASK 4 /* restore signal mask in do_signal() */ +#define TIF_NEED_RESCHED_LAZY 4 /* lazy rescheduling */ #define TIF_MEMDIE 5 /* is terminating due to OOM killer */ #define TIF_SYSCALL_TRACEPOINT 6 /* syscall tracepoint instrumentation */ #define TIF_SYSCALL_AUDIT 7 /* syscall auditing */ @@ -98,6 +99,7 @@ struct thread_info { #define TIF_NOTIFY_SIGNAL 9 /* signal notifications exist */ #define TIF_UPROBE 10 /* uprobe breakpoint or singlestep */ #define TIF_32BIT 11 /* compat-mode 32bit process */ +#define TIF_RESTORE_SIGMASK 12 /* restore signal mask in do_signal() */ #define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE) #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME) @@ -108,10 +110,11 @@ struct thread_info { #define _TIF_SECCOMP (1 << TIF_SECCOMP) #define _TIF_NOTIFY_SIGNAL (1 << TIF_NOTIFY_SIGNAL) #define _TIF_UPROBE (1 << TIF_UPROBE) +#define _TIF_NEED_RESCHED_LAZY (1 << TIF_NEED_RESCHED_LAZY) #define _TIF_WORK_MASK \ (_TIF_NOTIFY_RESUME | _TIF_SIGPENDING | _TIF_NEED_RESCHED | \ - _TIF_NOTIFY_SIGNAL | _TIF_UPROBE) + _TIF_NEED_RESCHED_LAZY | _TIF_NOTIFY_SIGNAL | _TIF_UPROBE) #define _TIF_SYSCALL_WORK \ (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_AUDIT | \ diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c index df9444397908..e38e33822f72 100644 --- a/arch/riscv/kernel/asm-offsets.c +++ b/arch/riscv/kernel/asm-offsets.c @@ -35,6 +35,7 @@ void asm_offsets(void) OFFSET(TASK_THREAD_S11, task_struct, thread.s[11]); OFFSET(TASK_TI_FLAGS, task_struct, thread_info.flags); OFFSET(TASK_TI_PREEMPT_COUNT, task_struct, thread_info.preempt_count); + OFFSET(TASK_TI_PREEMPT_LAZY_COUNT, task_struct, thread_info.preempt_lazy_count); OFFSET(TASK_TI_KERNEL_SP, task_struct, thread_info.kernel_sp); OFFSET(TASK_TI_USER_SP, task_struct, thread_info.user_sp); diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index b9eda3fcbd6d..595100a4c2c7 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -361,9 +361,14 @@ restore_all: resume_kernel: REG_L s0, TASK_TI_PREEMPT_COUNT(tp) bnez s0, restore_all - REG_L s0, TASK_TI_FLAGS(tp) - andi s0, s0, _TIF_NEED_RESCHED + REG_L s1, TASK_TI_FLAGS(tp) + andi s0, s1, _TIF_NEED_RESCHED + bnez s0, 1f + REG_L s0, TASK_TI_PREEMPT_LAZY_COUNT(tp) + bnez s0, restore_all + andi s0, s1, _TIF_NEED_RESCHED_LAZY beqz s0, restore_all +1: call preempt_schedule_irq j restore_all #endif
Implement the lazy preempt for riscv. Signed-off-by: Jisheng Zhang <jszhang@kernel.org> --- arch/riscv/Kconfig | 1 + arch/riscv/include/asm/thread_info.h | 7 +++++-- arch/riscv/kernel/asm-offsets.c | 1 + arch/riscv/kernel/entry.S | 9 +++++++-- 4 files changed, 14 insertions(+), 4 deletions(-)