From: Matthew R. Ochs Date: Wed, 21 Oct 2015 20:14:56 +0000 (-0500) Subject: cxlflash: Fix to prevent EEH recovery failure X-Git-Tag: firefly_0821_release~176^2~689^2~45 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=8e78262328ecfbe9d72ac40328ecf5e7ff6fc3bf;p=firefly-linux-kernel-4.4.55.git cxlflash: Fix to prevent EEH recovery failure The process_sense() routine can perform a read capacity which can take some time to complete. If an EEH occurs while waiting on the read capacity, the EEH handler will wait to obtain the context's mutex in order to put the context in an error state. The EEH handler will sit and wait until the context is free, but this wait can potentially last forever (deadlock) if the scsi_execute() that performs the read capacity experiences a timeout and calls into the reset callback. When that occurs, the reset callback sees that the device is already being reset and waits for the reset to complete. This leaves two threads waiting on the other. To address this issue, make the context unavailable to new, non-system owned threads and release the context while calling into process_sense(). After returning from process_sense() the context mutex is reacquired and the context is made available again. The context can be safely moved to the error state if needed during the unavailable window as no other threads will hold its reference. Signed-off-by: Matthew R. Ochs Signed-off-by: Manoj N. Kumar Reviewed-by: Brian King Reviewed-by: Daniel Axtens Reviewed-by: Tomas Henzl Signed-off-by: James Bottomley --- diff --git a/drivers/scsi/cxlflash/superpipe.c b/drivers/scsi/cxlflash/superpipe.c index e99a0eba42fa..d2309afe8c49 100644 --- a/drivers/scsi/cxlflash/superpipe.c +++ b/drivers/scsi/cxlflash/superpipe.c @@ -1787,12 +1787,21 @@ static int cxlflash_disk_verify(struct scsi_device *sdev, * inquiry (i.e. the Unit attention is due to the WWN changing). */ if (verify->hint & DK_CXLFLASH_VERIFY_HINT_SENSE) { + /* Can't hold mutex across process_sense/read_cap16, + * since we could have an intervening EEH event. + */ + ctxi->unavail = true; + mutex_unlock(&ctxi->mutex); rc = process_sense(sdev, verify); if (unlikely(rc)) { dev_err(dev, "%s: Failed to validate sense data (%d)\n", __func__, rc); + mutex_lock(&ctxi->mutex); + ctxi->unavail = false; goto out; } + mutex_lock(&ctxi->mutex); + ctxi->unavail = false; } switch (gli->mode) {