Subject: Re: [PATCH v2 09/30] cxlflash: Fix to stop interrupt processing on remove

From: Tomas Henzl <[email-masked]>
Date: Thu, 17 Sep 2015 14:38:19 +0200

On 16.9.2015 18:53, Matthew R. Ochs wrote:
> Interrupt processing can run in parallel to a remove operation. This
> can lead to a condition where the interrupt handler is processing with
> memory that has been freed.
>     
> To avoid processing an interrupt while memory may be yanked, check for
> removal while in the interrupt handler. Bail when removal is imminent.
>
> Signed-off-by: Matthew R. Ochs <[email-masked]>
> Signed-off-by: Manoj N. Kumar <[email-masked]>
> ---
>  drivers/scsi/cxlflash/common.h |  2 ++
>  drivers/scsi/cxlflash/main.c   | 21 +++++++++++++++------
>  2 files changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/scsi/cxlflash/common.h b/drivers/scsi/cxlflash/common.h
> index 1abe4e0..03d2cc6 100644
> --- a/drivers/scsi/cxlflash/common.h
> +++ b/drivers/scsi/cxlflash/common.h
> @@ -103,6 +103,8 @@ struct cxlflash_cfg {
>  	enum cxlflash_lr_state lr_state;
>  	int lr_port;
>  
> +	atomic_t remove_active;
> +
>  	struct cxl_afu *cxl_afu;
>  
>  	struct pci_pool *cxlflash_cmd_pool;
> diff --git a/drivers/scsi/cxlflash/main.c b/drivers/scsi/cxlflash/main.c
> index 6e85c77..89ee648 100644
> --- a/drivers/scsi/cxlflash/main.c
> +++ b/drivers/scsi/cxlflash/main.c
> @@ -892,6 +892,7 @@ static void cxlflash_remove(struct pci_dev *pdev)
>  	spin_unlock_irqrestore(&cfg->tmf_waitq.lock, lock_flags);
>  
>  	cfg->state = STATE_FAILTERM;
> +	atomic_inc(&cfg->remove_active);

Hi Matthew,
you could just call term_afu at this point, this way you don't
need an additional check in all irq functions.
Cheers,
Tomas

>  	cxlflash_stop_term_user_contexts(cfg);
>  
>  	switch (cfg->init_state) {
> @@ -1380,16 +1381,20 @@ static void afu_err_intr_init(struct afu *afu)
>  static irqreturn_t cxlflash_sync_err_irq(int irq, void *data)
>  {
>  	struct afu *afu = (struct afu *)data;
> +	struct cxlflash_cfg *cfg = afu->parent;
>  	u64 reg;
>  	u64 reg_unmasked;
>  
> +	if (atomic_read(&cfg->remove_active))
> +		goto out;
> +
>  	reg = readq_be(&afu->host_map->intr_status);
>  	reg_unmasked = (reg & SISL_ISTATUS_UNMASK);
>  
>  	if (reg_unmasked == 0UL) {
>  		pr_err("%s: %llX: spurious interrupt, intr_status %016llX\n",
>  		       __func__, (u64)afu, reg);
> -		goto cxlflash_sync_err_irq_exit;
> +		goto out;
>  	}
>  
>  	pr_err("%s: %llX: unexpected interrupt, intr_status %016llX\n",
> @@ -1397,7 +1402,7 @@ static irqreturn_t cxlflash_sync_err_irq(int irq, void *data)
>  
>  	writeq_be(reg_unmasked, &afu->host_map->intr_clear);
>  
> -cxlflash_sync_err_irq_exit:
> +out:
>  	pr_debug("%s: returning rc=%d\n", __func__, IRQ_HANDLED);
>  	return IRQ_HANDLED;
>  }
> @@ -1412,6 +1417,7 @@ cxlflash_sync_err_irq_exit:
>  static irqreturn_t cxlflash_rrq_irq(int irq, void *data)
>  {
>  	struct afu *afu = (struct afu *)data;
> +	struct cxlflash_cfg *cfg = afu->parent;
>  	struct afu_cmd *cmd;
>  	bool toggle = afu->toggle;
>  	u64 entry,
> @@ -1421,8 +1427,10 @@ static irqreturn_t cxlflash_rrq_irq(int irq, void *data)
>  
>  	/* Process however many RRQ entries that are ready */
>  	while (true) {
> -		entry = *hrrq_curr;
> +		if (atomic_read(&cfg->remove_active))
> +			goto out;
>  
> +		entry = *hrrq_curr;
>  		if ((entry & SISL_RESP_HANDLE_T_BIT) != toggle)
>  			break;
>  
> @@ -1440,7 +1448,7 @@ static irqreturn_t cxlflash_rrq_irq(int irq, void *data)
>  
>  	afu->hrrq_curr = hrrq_curr;
>  	afu->toggle = toggle;
> -
> +out:
>  	return IRQ_HANDLED;
>  }
>  
> @@ -1454,7 +1462,7 @@ static irqreturn_t cxlflash_rrq_irq(int irq, void *data)
>  static irqreturn_t cxlflash_async_err_irq(int irq, void *data)
>  {
>  	struct afu *afu = (struct afu *)data;
> -	struct cxlflash_cfg *cfg;
> +	struct cxlflash_cfg *cfg = afu->parent;
>  	u64 reg_unmasked;
>  	const struct asyc_intr_info *info;
>  	struct sisl_global_map *global = &afu->afu_map->global;
> @@ -1462,7 +1470,8 @@ static irqreturn_t cxlflash_async_err_irq(int irq, void *data)
>  	u8 port;
>  	int i;
>  
> -	cfg = afu->parent;
> +	if (atomic_read(&cfg->remove_active))
> +		goto out;
>  
>  	reg = readq_be(&global->regs.aintr_status);
>  	reg_unmasked = (reg & SISL_ASTATUS_UNMASK);