On 6/26/20 2:11 PM, Raviteja Narayanam wrote: Hi, [...] >> @@ -699,14 +708,7 @@ static int xiic_xfer(struct i2c_adapter *adap, struct >> i2c_msg *msgs, int num) >> if (err < 0) >> return err; >> >> - err = xiic_busy(i2c); >> - if (err) >> - goto out; >> - >> - i2c->tx_msg = msgs; >> - i2c->nmsgs = num; > > On an SMP system with multiple i2c-transfer command scripts running, the above critical section is expected to cause serious trouble overwriting the previous msg pointers. > But that's not happening as the i2c-core is having a lock at adapter level inside i2c-core-base.c (rt_mutex_lock_nested). > So, the race condition between different threads is not possible. They are all serialized by the locking in i2c-core. > > Although no issues are seen in the tests, the contention within the driver is still possible (isr vs xiic_xfer), if there is a spurious interrupt. And this patch is needed in that case. The contention happens between the threaded interrupt handler xiic_process() and this xiic_xfer() function. While you can not have xiic_xfer() running on two CPU cores at the same time, you can have xiic_xfer() running on one CPU core and xiic_process() on another CPU core, and that will lead to problems. [...]
