On Tue, 2018-12-04 at 23:48 +-0530, Kashyap Desai wrote: +AD4 Let me explain the issue. It is not a race, but very straight issue. Please clarify what makes you think that iterating over all requests does not race with request completion. Is request submission perhaps blocked during the firmware recovery process? Does the firmware recovery process wait for completion interrupts that are in progress to finish? +AD4 Let's +AD4 say we have one scsi+AF8-device /dev/sda and total IO submitted +- completed are +AD4 some number 100. +AD4 All the 100 IO is +ACo-completed+ACo. Now, As part of Firmware recovery, driver +AD4 tries to find our outstanding IOs using scsi+AF8-host+AF8-find+AF8-tag(). +AD4 Block layer will return all the 100 commands to the driver but really those +AD4 100 commands are not outstanding. This patch will return +ACo-actual+ACo +AD4 outstanding commands. Would iterating over started requests be a good alternative to the patch that you had posted? The header above blk+AF8-mq+AF8-tagset+AF8-busy+AF8-iter() is as follows (this function is used by e.g. the skd driver for firmware recovery): /+ACoAKg +ACo blk+AF8-mq+AF8-tagset+AF8-busy+AF8-iter - iterate over all started requests in a tag set +ACo +AEA-tagset: Tag set to iterate over. +ACo +AEA-fn: Pointer to the function that will be called for each started +ACo request. +AEA-fn will be called as follows: +AEA-fn(rq, +AEA-priv, +ACo reserved) where rq is a pointer to a request. 'reserved' +ACo indicates whether or not +AEA-rq is a reserved request. +ACo +AEA-priv: Will be passed as second argument to +AEA-fn. +ACo-/ +AD4 I am not able to find right context from srp, but I check the srp code and +AD4 looks like that driver is getting scmd using scsi+AF8-host+AF8-find+AF8-tag() for live +AD4 command. Sorry, my e-mail was a bit too short to be comprehensible. When running sg+AF8-reset -d /dev/sd... in a loop it is possible that the SCSI reset handler terminates a request while the SRP driver is handling a request completion for one of the terminated requests. That is why both srp+AF8-process+AF8-srp() and the reset handler call srp+AF8-claim+AF8-req() to make sure that only one of these two contexts completes a request. Bart.
