An EAGAIN error when writing from kernel to user space app

Asked Jan 25 '18 at 13:01

Active Jan 25 '18 at 13:01

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I have this issue, that happens once in a while for no clear reason: I have kernel module, that sends messages to user space deamon application using genlmsg_unicast(). After some time, all messages start to fail and the error code is -11 (EAGAIN). And there's no way to get out of this. Even if I restart the user application. Also, I don't see any error on the receiving side in the application. It just stops receiving packets. Can somebody advise?

Thank you, Mark

asked Jan 25 '18 at 13:01

user2613815

seems like you are filling up the buffer queue even before the userspace has consumed it. you need to either increase the buffer size or do a handshake with kernel/userpace. – Prabhakar Lad Jan 25 '18 at 13:06
Hi, Thank you for the quick answer. – user2613815 Jan 25 '18 at 13:33
What do you mean "do a handshake"? – user2613815 Jan 25 '18 at 13:33
notify the kernel from userspace you have read the buffer so that you can fill in a new one. – Prabhakar Lad Jan 25 '18 at 13:37
The question is, why doesn't the queue get cleaned up once I restart the user space application? – user2613815 Jan 25 '18 at 13:45

An EAGAIN error when writing from kernel to user space app

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