risc-v/mpfs: ihc: don't wait for a remote ack #144
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RPMSG is associated with the use of HPWORK / LPWORK queues. After sending a message to the remote end (Linux), it waits for an ack before proceeding. Unfortunately this may take sometimes more than 0x3000 CLINT MTIME cycles. Ack waiting is also unnecessary: nothing is done with that information. Even worse, the net_lock() is also held during the blocked time so it blocks other network stacks that are unrelated to this. The logic is still maintained with the message present (MP) flag. No new message will be sent until that is cleared by the romote. Signed-off-by: Eero Nurkkala <[email protected]>
jlaitine
approved these changes
Aug 9, 2023
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RPMSG is associated with the use of HPWORK / LPWORK queues. After sending a message to the remote end (Linux), it waits for an ack before proceeding.
Unfortunately this may take sometimes more than 0x3000 CLINT MTIME cycles. Ack waiting is also unnecessary: nothing is done with that information. Even worse, the net_lock() is also held during the blocked time so it blocks other network stacks that are unrelated to this.
The logic is still maintained (without the ack) with the message present (MP) flag. No new message will be sent until that is cleared by the remote.
Summary
It looks like the ihc breaks the network stack by blocking within the HPWORK/LPWORK with net_lock() taken. What happens eventually:
Impact
All RPMSG client / servers
Testing
So far more than 6 hours with no problems (earlier: happening 100% < 3 hrs)