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riscv: Don't reschedule on back-to-back interrupts

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In some cases the 'reschedule' code path is executed when the current
thread is the same as the next thread in the ready Q. If this happens,
the swap_return_value of the thread is ifalsely being reset to -EAGAIN.

This commit prevents the rescheduling code to run if the current thread
is the same as the thread in the ready Q.

Signed-off-by: Wolfgang Reißnegger <gnagflow@fb.com>
This commit is contained in:
Wolfgang Reißnegger 2021-05-24 14:36:28 -07:00 committed by Anas Nashif
parent 164029b0c5
commit 535fc38fe7
1 changed files with 12 additions and 0 deletions
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12
arch/riscv/core/isr.S
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@ -811,6 +811,18 @@ skip_fp_move_irq:
#endif /* CONFIG_USERSPACE */
reschedule:
/*
* Check if the current thread is the same as the thread on the ready Q. If
* so, do not reschedule.
* Note:
* Sometimes this code is execute back-to-back before the target thread
* has a chance to run. If this happens, the current thread and the
* target thread will be the same.
*/
la t0, _kernel
RV_OP_LOADREG t2, _kernel_offset_to_current(t0)
RV_OP_LOADREG t3, _kernel_offset_to_ready_q_cache(t0)
beq t2, t3, no_reschedule
#if CONFIG_INSTRUMENT_THREAD_SWITCHING
call z_thread_mark_switched_out