michaelh/zephyr
1
0
Fork 0
Code Releases Activity

riscv: isr.S: compute _current_cpu using CPU number on SMP

Browse source 
To do so efficiently on systems without the mul instruction, we use
shifts and adds which is faster and sometimes smaller than a plain loop.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
This commit is contained in:
Nicolas Pitre 2022-03-09 23:47:38 -05:00 • committed by Anas Nashif
commit af2d875c5d
2 changed files with 40 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

18
arch/riscv/core/isr.S
View file

@ -59,6 +59,16 @@
op a6, __z_arch_esf_t_a6_OFFSET(sp) ;\
op a7, __z_arch_esf_t_a7_OFFSET(sp) ;
#ifdef CONFIG_SMP
#define GET_CURRENT_CPU(dst, tmp) \
csrr tmp, mhartid ;\
la dst, _kernel + ___kernel_t_cpus_OFFSET ;\
shiftmul_add dst, tmp, ___cpu_t_SIZEOF
#else
#define GET_CURRENT_CPU(dst, tmp) \
la dst, _kernel + ___kernel_t_cpus_OFFSET
#endif
#define ASSUME_EQUAL(x, y) .if x != y; .err; .endif
/* imports */
@ -137,7 +147,7 @@ SECTION_FUNC(exception.entry, __irq_wrapper)
/* Save s0 in the esf and load it with &_current_cpu. */
sr s0, __z_arch_esf_t_s0_OFFSET(sp)
la s0, _kernel + ___kernel_t_cpus_OFFSET
GET_CURRENT_CPU(s0, t0)
#ifdef CONFIG_USERSPACE
/*
@ -448,8 +458,10 @@ reschedule:
z_riscv_thread_start:
might_have_rescheduled:
/* SMP note: reload s0 with &_current_cpu as it might have changed */
#ifdef CONFIG_SMP
/* reload s0 with &_current_cpu as it might have changed */
GET_CURRENT_CPU(s0, t0)
#endif
no_reschedule: