chirping78 commented on PR #15985: URL: https://github.com/apache/nuttx/pull/15985#issuecomment-2728509964
@sdc-g I have some concerns about your this PR. Without your PR, in new task‘s register save area, REG_PS's `EXCM` bit is clear. Before the new task is resumed , `exception_exit` will copy REG_PS from register save area to PS (for level1) or EPS[N] (for level2 and above). - if new task be resumed by level1: `rfe` sets PS.EXCM back to 0, and then jumps to the address in EPC[1]. To prevent the resuming action be interrupted, REG_PS.EXCM is set to 1 [here](https://github.com/apache/nuttx/blob/master/arch/xtensa/src/common/xtensa_user_handler.S#L317) and [here](https://github.com/apache/nuttx/blob/master/arch/xtensa/src/common/xtensa_int_handlers.S#L224) - if new task be resumed by level2 and above: `rfi` will restores the PS from EPS[N] and jump to the address in EPC[N]. ---------------------- Now with your PR, in new task‘s register save area, REG_PS's `EXCM` bit is set. - If new task be resumed by level1: `rfe` sets PS.EXCM back to 0, and then jumps to the address in EPC[1]. No problem here, it works as before. - If new task be resumed by level2 and above: `rfi` will restores the PS from EPS[N] and jump to the address in EPC[N]. ***Problem will be here***, after the new task be resumed, ***the PS.EXCM bit is still set***. If window rotation related instruction is executed, error will arise. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: commits-unsubscr...@nuttx.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
