Bug 205533

Summary: The flexcan/socketcan driver does not block and returns an error if all buffers are in use on transmit.
Product: Networking Reporter: Brian Cody (brian.j.cody)
Component: OtherAssignee: Stephen Hemminger (stephen)
Status: NEW ---    
Severity: low    
Priority: P1    
Hardware: ARM   
OS: Linux   
Kernel Version: 4.14.149 Subsystem:
Regression: No Bisected commit-id:

Description Brian Cody 2019-11-14 17:10:29 UTC 
When the output buffer is saturated, even if the socket is set up for blocking use, a "write" to the CAN socket may result in a -1 return value with errno set to 105 (ENOBUFS).

The socket is created using socket(PF_CAN, SOCK_RAW, CAN_RAW). SO_SNDBUF is set to 2240. fcntl is used to disable O_NONBLOCK.

I see the error case after "many" sends. In this situation three separate processes are sharing the CAN bus on the local processor. The error only occurs when all processes are heavily using the bus (set at 1 MHz), and there does not appear to be a normal re-entrancy issue with the driver.