Multi-threads in pta

[hikrisyy]

Hello

I hava some questiones about multi-threads in pta.

1. If op-tee runs on a hardware platform with 4 CPU cores, whether the PTA can run on different CPU cores in parallel when two REE threads invoke one PTA at a same time?
2. If op-tee runs on a hardware platform with one CPU core, when two REE threads invoke one PTA at a same time, how to handle in PTA? The scheduler is in tee or ree?

[ivila]

1. If op-tee runs on a hardware platform with 4 CPU cores, whether the PTA can run on different CPU cores in parallel when two REE threads invoke one PTA at a same time?

I think all the current PTAs in optee-os defined SINGLE_INSTANCE | MULTIPLE_SESSION | KEEP_ALIVE (check this link)
So, they can invoke the PTA at the same time.
Check this for what those properties means: optee.readthedocs.io-properties

2. If op-tee runs on a hardware platform with one CPU core, when two REE threads invoke one PTA at a same time, how to handle in PTA? The scheduler is in tee or ree?

1. If a PTA defines TA_FLAG_CONCURRENT, the requests would be handle concurrently (check this commit for detail), for example, pta hwrng defines it so you can call it concurrently.
2. If a PTA doesn't define TA_FLAG_CONCURRENT, the requests would be handle sequentially (however, you can still make them run concurrently by CFG_CONCURRENT_SINGLE_INSTANCE_TA=y when compiling optee_os, check this commit for detail)

And linux kernel do the schedule job of REE, there is no scheduling in TEE.

For more about scheduling, you may check:

1. optee.readthedocs.io-trusted-thread-scheduling
2. Questions about TA concurrency #5983

[sunnybird]

Hello,
I did some research on this issue.

the TA can run on different CPU cores , depends REE scheduler.
but , two REE threads invoke the TA not in parallel. this call will execute one by one .

when thread 1 is doing invoke , the thread 2 will wait until thread 1 finish .

releated code ：
https://github.com/OP-TEE/optee_os/blob/master/core/tee/entry_std.c#L431
https://github.com/OP-TEE/optee_os/blob/master/core/kernel/tee_ta_manager.c#L261

[gagachang]

when thread 1 is doing invoke , the thread 2 will wait until thread 1 finish .

Maybe you need to open two sessions, session 1 for thread 1 and session 2 for thread 2 ?