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| author | Vincent Chen <vincentc@andestech.com> | 2019-01-03 11:32:33 +0800 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@sifive.com> | 2019-01-23 12:56:19 -0800 |
| commit | 99fd6e875d0c24448a5e2c241422a691be46b241 (patch) | |
| tree | 4b253b38db1d5a3653ef38fd01d3fb0599c877de | |
| parent | 49a57857aeea06ca831043acbb0fa5e0f50602fd (diff) | |
| download | linux-99fd6e875d0c24448a5e2c241422a691be46b241.tar.bz2 | |
RISC-V: Add _TIF_NEED_RESCHED check for kernel thread when CONFIG_PREEMPT=y
The cond_resched() can be used to yield the CPU resource if
CONFIG_PREEMPT is not defined. Otherwise, cond_resched() is a dummy
function. In order to avoid kernel thread occupying entire CPU,
when CONFIG_PREEMPT=y, the kernel thread needs to follow the
rescheduling mechanism like a user thread.
Signed-off-by: Vincent Chen <vincentc@andestech.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
| -rw-r--r-- | arch/riscv/kernel/asm-offsets.c | 1 | ||||
| -rw-r--r-- | arch/riscv/kernel/entry.S | 18 |
2 files changed, 18 insertions, 1 deletions
diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c index 6a92a2fe198e..dac98348c6a3 100644 --- a/arch/riscv/kernel/asm-offsets.c +++ b/arch/riscv/kernel/asm-offsets.c @@ -39,6 +39,7 @@ void asm_offsets(void) OFFSET(TASK_STACK, task_struct, stack); OFFSET(TASK_TI, task_struct, thread_info); OFFSET(TASK_TI_FLAGS, task_struct, thread_info.flags); + OFFSET(TASK_TI_PREEMPT_COUNT, task_struct, thread_info.preempt_count); OFFSET(TASK_TI_KERNEL_SP, task_struct, thread_info.kernel_sp); OFFSET(TASK_TI_USER_SP, task_struct, thread_info.user_sp); OFFSET(TASK_TI_CPU, task_struct, thread_info.cpu); diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index 355166f57205..fd9b57c8b4ce 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -144,6 +144,10 @@ _save_context: REG_L x2, PT_SP(sp) .endm +#if !IS_ENABLED(CONFIG_PREEMPT) +.set resume_kernel, restore_all +#endif + ENTRY(handle_exception) SAVE_ALL @@ -228,7 +232,7 @@ ret_from_exception: REG_L s0, PT_SSTATUS(sp) csrc sstatus, SR_SIE andi s0, s0, SR_SPP - bnez s0, restore_all + bnez s0, resume_kernel resume_userspace: /* Interrupts must be disabled here so flags are checked atomically */ @@ -250,6 +254,18 @@ restore_all: RESTORE_ALL sret +#if IS_ENABLED(CONFIG_PREEMPT) +resume_kernel: + REG_L s0, TASK_TI_PREEMPT_COUNT(tp) + bnez s0, restore_all +need_resched: + REG_L s0, TASK_TI_FLAGS(tp) + andi s0, s0, _TIF_NEED_RESCHED + beqz s0, restore_all + call preempt_schedule_irq + j need_resched +#endif + work_pending: /* Enter slow path for supplementary processing */ la ra, ret_from_exception |