I reported the same problem earlier and was told that this was by design. Earlier thread: https://lists.trustedfirmware.org/archives/list/tf-m@lists.trustedfirmware.o...
-Joakim
From: Bohdan.Hunko--- via TF-M tf-m@lists.trustedfirmware.org Sent: mandag 13. mars 2023 15:17 To: tf-m@lists.trustedfirmware.org Cc: Roman.Mazurak@infineon.com Subject: [TF-M] Scheduler problem
Caution: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
Hi everyone,
Why investigation some interrupts related stuff I have noticed a problem/bug in the scheduler. PendSV_Handler has following code: " movs r0, #"M2S(EXC_RETURN_SECURE_STACK)" \n" " mov r1, lr \n" " tst r0, r1 \n" /* NS interrupted */ " beq v8b_pendsv_exit \n" /* No schedule */ Which means that if NSPE was interrupted then no scheduling will be done. This created a problem in following scenario:
1. NSPE is executing 2. Secure interrupts arrives. 3. NSPE is interrupted, secure interrupt is handled. 4. Secure interrupts triggers scheduling of some partition. 5. Secure interrupt returns 6. Scheduling is triggered 7. PendSV returns (because /* NS interrupted */ /* No schedule */ ) and does not perform scheduling even thought pending partition is present. This means that pending partition will only be scheduled when next PSA call will be done be NSPE. Even if there would be subsequent Secure interrupts that preempt NSPE, partition will not be scheduled because PendSV will always return without scheduling because NSPE was interrupted.
I was not able to find any information about this in TFM docs so I assume this is a bug.
Please let me know if I am wrong. And if this is real problem then is there a plan to fix this?
Regards, Bohdan Hunko
Cypress Semiconductor Ukraine Engineer CSUKR CSS ICW SW FW Mobile: +38099 50 19 714 Bohdan.Hunko@infineon.commailto:Bohdan.Hunko@infineon.com