| Message ID | 1428825578-12326-1-git-send-email-anders.roxell@linaro.org |
|---|---|
| State | New |
| Headers | show |
On 2015-04-13 16:02, Sebastian Andrzej Siewior wrote: > * Anders Roxell | 2015-04-12 09:59:38 [+0200]: > > >arm64 is missing support for PREEMPT_RT. The main feature which is > >lacking is support for lazy preemption. The arch-specific entry code, > >thread information structure definitions, and associated data tables > >have to be extended to provide this support. Then the Kconfig file has > >to be extended to indicate the support is available, and also to > >indicate that support for full RT preemption is now available. > > > >Signed-off-by: Anders Roxell <anders.roxell@linaro.org> > >--- > > > >I tested this on an arm64 juno target, to get that to boot I had to > >backport the dtb from v4.0-rc6 to v3.18.11-rt6. > > Seriously? It all works by itself? I would say yes, but now you get me wondering... =) > Out of curiosity, how likely is it > that I can login on one of these machines if I send you a ssh key? I will look into that. > > > arch/arm64/Kconfig | 2 ++ > > arch/arm64/include/asm/thread_info.h | 3 +++ > > arch/arm64/kernel/asm-offsets.c | 1 + > > arch/arm64/kernel/entry.S | 14 ++++++++++---- > > 4 files changed, 16 insertions(+), 4 deletions(-) > > > >diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > >index 9532f8d..62f4e00 100644 > >--- a/arch/arm64/Kconfig > >+++ b/arch/arm64/Kconfig > >@@ -59,7 +59,9 @@ config ARM64 > > select HAVE_PERF_REGS > > select HAVE_PERF_USER_STACK_DUMP > > select HAVE_RCU_TABLE_FREE > >+ select HAVE_PREEMPT_LAZY > > select HAVE_SYSCALL_TRACEPOINTS > >+ select IRQ_FORCED_THREADING > > Did you mark all non-threadable interrupts? Commit da0ec6f7c1e ("ARM: > 7814/2: Allow forced irq threading") was the patch for ARM. If so you > could take this piece and send upstream and get the kernel commandline > "threadirqs" working without -RT :) I will try to do that. > > For the lazy-preempt pieces, arch/arm64/kernel/entry.S, work_pending > checks only for TIF_NEED_RESCHED while arm checks for both (this and > _TIF_NEED_RESCHED_LAZY). You sure you don't need it? I'm have my doubts now, I have to investigate that. > > Sebastian Cheers, Anders -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 9532f8d..62f4e00 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -59,7 +59,9 @@ config ARM64 select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP select HAVE_RCU_TABLE_FREE + select HAVE_PREEMPT_LAZY select HAVE_SYSCALL_TRACEPOINTS + select IRQ_FORCED_THREADING select IRQ_DOMAIN select MODULES_USE_ELF_RELA select NO_BOOTMEM diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 459bf8e..3e24ea1 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -50,6 +50,7 @@ struct thread_info { struct exec_domain *exec_domain; /* execution domain */ struct restart_block restart_block; int preempt_count; /* 0 => preemptable, <0 => bug */ + int preempt_lazy_count; /* 0 => preemptable, <0 => bug */ int cpu; /* cpu */ }; @@ -108,6 +109,7 @@ static inline struct thread_info *current_thread_info(void) #define TIF_NEED_RESCHED 1 #define TIF_NOTIFY_RESUME 2 /* callback before returning to user */ #define TIF_FOREIGN_FPSTATE 3 /* CPU's FP state is not current's */ +#define TIF_NEED_RESCHED_LAZY 4 #define TIF_NOHZ 7 #define TIF_SYSCALL_TRACE 8 #define TIF_SYSCALL_AUDIT 9 @@ -124,6 +126,7 @@ static inline struct thread_info *current_thread_info(void) #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME) #define _TIF_FOREIGN_FPSTATE (1 << TIF_FOREIGN_FPSTATE) +#define _TIF_NEED_RESCHED_LAZY (1 << TIF_NEED_RESCHED_LAZY) #define _TIF_NOHZ (1 << TIF_NOHZ) #define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE) #define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT) diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index 9a9fce0..f774136 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -36,6 +36,7 @@ int main(void) BLANK(); DEFINE(TI_FLAGS, offsetof(struct thread_info, flags)); DEFINE(TI_PREEMPT, offsetof(struct thread_info, preempt_count)); + DEFINE(TI_PREEMPT_LAZY, offsetof(struct thread_info, preempt_lazy_count)); DEFINE(TI_ADDR_LIMIT, offsetof(struct thread_info, addr_limit)); DEFINE(TI_TASK, offsetof(struct thread_info, task)); DEFINE(TI_EXEC_DOMAIN, offsetof(struct thread_info, exec_domain)); diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 726b910..8a631bb 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -347,11 +347,16 @@ el1_irq: #ifdef CONFIG_PREEMPT get_thread_info tsk ldr w24, [tsk, #TI_PREEMPT] // get preempt count - cbnz w24, 1f // preempt count != 0 + cbnz w24, 2f // preempt count != 0 ldr x0, [tsk, #TI_FLAGS] // get flags - tbz x0, #TIF_NEED_RESCHED, 1f // needs rescheduling? - bl el1_preempt + tbz x0, #_TIF_NEED_RESCHED, 2f // needs rescheduling? + + ldr w24, [tsk, #TI_PREEMPT_LAZY] // get preempt lazy count + cbnz w24, 1f // preempt count != 0 + tbz x0, #_TIF_NEED_RESCHED_LAZY, 2f // needs rescheduling? 1: + bl el1_preempt +2: #endif #ifdef CONFIG_TRACE_IRQFLAGS bl trace_hardirqs_on @@ -364,7 +369,8 @@ el1_preempt: mov x24, lr 1: bl preempt_schedule_irq // irq en/disable is done inside ldr x0, [tsk, #TI_FLAGS] // get new tasks TI_FLAGS - tbnz x0, #TIF_NEED_RESCHED, 1b // needs rescheduling? + tbnz x0, #_TIF_NEED_RESCHED, 2b // needs rescheduling? + tbnz x0, #_TIF_NEED_RESCHED_LAZY, 2b ret x24 #endif
arm64 is missing support for PREEMPT_RT. The main feature which is lacking is support for lazy preemption. The arch-specific entry code, thread information structure definitions, and associated data tables have to be extended to provide this support. Then the Kconfig file has to be extended to indicate the support is available, and also to indicate that support for full RT preemption is now available. Signed-off-by: Anders Roxell <anders.roxell@linaro.org> --- I tested this on an arm64 juno target, to get that to boot I had to backport the dtb from v4.0-rc6 to v3.18.11-rt6. arch/arm64/Kconfig | 2 ++ arch/arm64/include/asm/thread_info.h | 3 +++ arch/arm64/kernel/asm-offsets.c | 1 + arch/arm64/kernel/entry.S | 14 ++++++++++---- 4 files changed, 16 insertions(+), 4 deletions(-)