[PATCH] mmc: race condition between "sdcard hot plug out" and "system reboot"

[Joe.Zhou]

From: Joe Zhou <Joe.Zhou at mediatek.com>

> Thanks for your patch!

> Doesn't commit 66c915d09b94 ("mmc: core: Disable card detect during
> shutdown") take care of this problem?

> Kind regards
> Uffe


Dear Ulf,
     Thank you for your replay!

     I think that commit66c915d09b94 ("mmc: core: Disable card detect during shutdown") doesn't reslove this issue.
     1. Issues may asise in the following processing.
     sdcard hot pulg out:                                  SyS_reboot:
     CPU0                                                  CPU1
     _mmc_detect_change() {
     ......
     mmc_schedule_delayed_work(&host->detect, delay)
     #Step1: call delay work &host->detect
         mmc_rescan()
         {
          .......
              #Step2: detect SD card removed
              mmc_sd_detect() {                              ......
                                                             _mmc_stop_host (.pre_shutdown)
                                                            {
              ......                                        #Step3:_mmc_stop_host() cancel detect use sync
                                                            cancel_delayed_work_sync(&host->detect)
                                                            #Step4: wait delay work complete
                                                            }
                 if (err) {
                 #Step5: host->card is NULL
                 mmc_sd_remove(host);                        ......
                                                            #Step6: wait delay work complete
                                                            mmc_sd_suspend (.shutdown)
                                                            {
                                                             ......

                                                            #Step7:_mmc_sd_suspend claimed host
                                                            mmc_claim_host(host);
                                                            #Step8: use host-card(NULL pointer)
                                                            if (mmc_card_suspended(host->card))
                                                             ......
                                                            }
                 mmc_claim_host(host);
                 mmc_detach_bus(host);
                }
             }
          }
       ......
      }

     2. And in the version that includes the patch, we have reproduced the issue.

Best regards,
Joe