Messages in this thread | | | Date | Thu, 17 Aug 2023 15:41:55 +0800 | Subject | Re: [PATCH] scsi: ata: Fix a race condition between scsi error handler and ahci interrupt | From | Li Nan <> |
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在 2023/8/15 10:41, Damien Le Moal 写道: > On 8/14/23 22:20, Li Nan wrote: >> >> 在 2023/8/14 15:50, Damien Le Moal 写道: >>> On 8/14/23 15:41, Li Nan wrote: >>>>> This is definitely not correct because EH may have been scheduled for a non >>>>> fatal action like a device revalidate or to get sense data for successful >>>>> commands. With this change, the port will NOT be frozen when a hard error IRQ >>>>> comes while EH is waiting to start, that is, while EH waits for all commands to >>>>> complete first. >>>>> >>>> >>>> Yeah, we should find a better way to fix it. Do you have any suggesstions? >>>> >>>>> Furthermore, if you get an IRQ that requires the port to be frozen, it means >>>>> that you had a failed command. In that case, the drive is in error state per >>>>> ATA specs and stops all communication until a read log 10h command is issued. >>>>> So you should never ever see 2 error IRQs one after the other. If you do, it >>>>> very likely means that you have buggy hardware. >>>>> >>>>> How do you get into this situation ? What adapter and disk are you using ? >>>>> >>>> >>>> > How do you get into this situation ? >>>> The first IRQ is io error, the second IRQ is disk link flash break. >>> >>> What does "link flash break" mean ? >>> >>>> >>>> > What adapter and disk are you using ? >>>> It is a disk developed by our company, but we think the same issue >>>> exists when using other disks. >>> >>> As I said, I find this situation highly suspect because if the first IRQ was to >>> signal an IO error that the drive reported, then per ATA specifications, the >>> drive should be in error mode and should NOT have transmitted any other FIS >>> after the SDB FIS that signaled the error. Nothing at all should come after that >>> error SDB FIS, until the host issues a read log 10h to get thee drive out of >>> error state. >>> >>> If this is a prototype device, I would recommend that you take an ATA bus trace >>> and verify the FIS traffic. Something fishy is going on with the drive in my >>> opinion. >>> >> >> Thank you for your patient explanation. I'm sorry I didn't explain the >> problem clearly before. After discussing with my colleagues who know >> more about dirvers, Let me re-describe the problem. >> >> The problem`s situation is the SATA link is quickly disconnected and >> connected. For example, when an I/O error is processed in error handling >> thread, the disk is manually removed and inserted, and the AHCI chip >> reports a hot plug interrupt. >> >> This scenario is not just an NCQ error, but a disk is removed and >> quickly inserted before the error processing is completed. For the error >> handling process, the disk status needs to be restored after the error >> handling is complete. > > In your original email, you showed: > > interrupt scsi_eh > > ahci_error_intr > =>ata_port_freeze > =>__ata_port_freeze > =>ahci_freeze (turn IRQ off) > =>ata_port_abort > =>ata_port_schedule_eh > =>shost->host_eh_scheduled++; > host_eh_scheduled = 1 > scsi_error_handler > =>ata_scsi_error > =>ata_scsi_port_error_handler > =>ahci_error_handler > . =>sata_pmp_error_handler > . =>ata_eh_thaw_port > . =>ahci_thaw (turn IRQ on) > ahci_error_intr . > =>ata_port_freeze . > =>__ata_port_freeze . > =>ahci_freeze (turn IRQ off) . > =>ata_port_abort . > =>ata_port_schedule_eh . > =>shost->host_eh_scheduled++; . > host_eh_scheduled = 2 . > > But here, I do not understand how host_eh_scheduled can be incremented since the > shost state should still be SHOST_RECOVERY until scsi_restart_operations() is > called at the end of scsi_error_handler(), which is after ata_std_end_eh() is > executed toward the end of ata_scsi_port_error_handler().
Yeah, shost state is still SHOST_RECOVERY during this period. But I don't think this will affect host_eh_scheduled++. In scsi_host_set_state(), if (state == old state), it will return 0. So: ata_port_schedule_eh ata_std_sched_eh scsi_schedule_eh if (scsi_host_set_state(shost, SHOST_RECOVERY) == 0) -> true shost->host_eh_scheduled++
> Not sure how what you are showing here can happen. Can you have a closer look ? > > =>ata_std_end_eh > =>host->host_eh_scheduled = 0; > > In any case, for you particular failure pattern, given that the disk "goes away" > while EH is running, I would expect the commands executed during EH (e.g. read > log 10h) to timeout, which would cause a reset and a revalidate after that. The
If we remove the disk when EH is abount to end (after 'ahci_thaw'), the commands which needed to be executed on the disk has already been completed, and EH will not time out.
> reset should clear the port interrupt error bits, which should allow everything > to recover after aborting all commands caught by the first EH run. >
-- Thanks, Nan
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