[PATCH AUTOSEL for 4.4 048/101] scsi: mac_esp: Replace bogus memory barrier with spinlock

Sasha Levin
2018-03-08T05:06:15Z

From: Finn Thain <fthain@telegraphics.com.au>

[ Upstream commit 4da2b1eb230ba4ad19b58984dc52e05b1073df5f ]

Commit da244654c66e ("[SCSI] mac_esp: fix for quadras with two esp
chips") added mac_scsi_esp_intr() to handle the IRQ lines from a pair of
on-board ESP chips (a normal shared IRQ did not work).

Proper mutual exclusion was missing from that patch. This patch fixes
race conditions between comparison and assignment of esp_chips[]
pointers.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Reviewed-by: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
drivers/scsi/mac_esp.c | 33 +++++++++++++++++++++++----------
1 file changed, 23 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/mac_esp.c b/drivers/scsi/mac_esp.c
index 14c0334f41e4..26c67c42985c 100644
--- a/drivers/scsi/mac_esp.c
+++ b/drivers/scsi/mac_esp.c
@@ -55,6 +55,7 @@ struct mac_esp_priv {
int error;
};
static struct esp *esp_chips[2];
+static DEFINE_SPINLOCK(esp_chips_lock);

#define MAC_ESP_GET_PRIV(esp) ((struct mac_esp_priv *) \
platform_get_drvdata((struct platform_device *) \
@@ -562,15 +563,18 @@ static int esp_mac_probe(struct platform_device *dev)
}

host->irq = IRQ_MAC_SCSI;
- esp_chips[dev->id] = esp;
- mb();
- if (esp_chips[!dev->id] == NULL) {
- err = request_irq(host->irq, mac_scsi_esp_intr, 0, "ESP", NULL);
- if (err < 0) {
- esp_chips[dev->id] = NULL;
- goto fail_free_priv;
- }
+
+ /* The request_irq() call is intended to succeed for the first device
+ * and fail for the second device.
+ */
+ err = request_irq(host->irq, mac_scsi_esp_intr, 0, "ESP", NULL);
+ spin_lock(&esp_chips_lock);
+ if (err < 0 && esp_chips[!dev->id] == NULL) {
+ spin_unlock(&esp_chips_lock);
+ goto fail_free_priv;
}
+ esp_chips[dev->id] = esp;
+ spin_unlock(&esp_chips_lock);

err = scsi_esp_register(esp, &dev->dev);
if (err)
@@ -579,8 +583,13 @@ static int esp_mac_probe(struct platform_device *dev)
return 0;

fail_free_irq:
- if (esp_chips[!dev->id] == NULL)
+ spin_lock(&esp_chips_lock);
+ esp_chips[dev->id] = NULL;
+ if (esp_chips[!dev->id] == NULL) {
+ spin_unlock(&esp_chips_lock);
free_irq(host->irq, esp);
+ } else
+ spin_unlock(&esp_chips_lock);
fail_free_priv:
kfree(mep);
fail_free_command_block:
@@ -599,9 +608,13 @@ static int esp_mac_remove(struct platform_device *dev)

scsi_esp_unregister(esp);

+ spin_lock(&esp_chips_lock);
esp_chips[dev->id] = NULL;
- if (!(esp_chips[0] || esp_chips[1]))
+ if (esp_chips[!dev->id] == NULL) {
+ spin_unlock(&esp_chips_lock);
free_irq(irq, NULL);
+ } else
+ spin_unlock(&esp_chips_lock);

kfree(mep);

--
2.14.1