Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750881AbdDBHEn (ORCPT ); Sun, 2 Apr 2017 03:04:43 -0400 Received: from kvm5.telegraphics.com.au ([98.124.60.144]:59220 "EHLO kvm5.telegraphics.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750783AbdDBHEm (ORCPT ); Sun, 2 Apr 2017 03:04:42 -0400 Date: Sun, 02 Apr 2017 17:08:05 +1000 To: "James E.J. Bottomley" , "Martin K. Petersen" Cc: , Message-Id: <1ecb1ec37388c616335dba37b42b4a7676df6c1e.1491115954.git.fthain@telegraphics.com.au> From: Finn Thain Subject: [PATCH] scsi/mac_esp: Replace bogus memory barrier with spinlock Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2455 Lines: 84 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 --- 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 14c0334..586efd1 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); -- 2.10.2