[PATCH 06/11] staging: kpc2000: use atomic_t to assign card numbers.

Jeremy Sowden jeremy at azazel.net
Thu May 16 20:04:06 UTC 2019


Previously the next card number was assigned from a static int local
variable, which was read and later incremented.  This was not thread-
safe, so now we use an atomic_t and atomic_fetch_add instead.

Updated TODO.

Signed-off-by: Jeremy Sowden <jeremy at azazel.net>
---
 drivers/staging/kpc2000/TODO           | 1 -
 drivers/staging/kpc2000/kpc2000/core.c | 7 ++++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/kpc2000/TODO b/drivers/staging/kpc2000/TODO
index 669fe5bf9637..47530e23e940 100644
--- a/drivers/staging/kpc2000/TODO
+++ b/drivers/staging/kpc2000/TODO
@@ -1,6 +1,5 @@
 - the kpc_spi driver doesn't seem to let multiple transactions (to different instances of the core) happen in parallel...
 - The kpc_i2c driver is a hot mess, it should probably be cleaned up a ton.  It functions against current hardware though.
-- pcard->card_num in kp2000_pcie_probe() is a global variable and needs atomic / locking / something better.
 - would be nice if the AIO fileops in kpc_dma could be made to work
     - probably want to add a CONFIG_ option to control compilation of the AIO functions
 - if the AIO fileops in kpc_dma start working, next would be making iov_count > 1 work too
diff --git a/drivers/staging/kpc2000/kpc2000/core.c b/drivers/staging/kpc2000/kpc2000/core.c
index eb8bac62d33d..72130a50afd6 100644
--- a/drivers/staging/kpc2000/kpc2000/core.c
+++ b/drivers/staging/kpc2000/kpc2000/core.c
@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0+
+#include <linux/atomic.h>
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/pci.h>
@@ -19,6 +20,8 @@
 #include "pcie.h"
 
 
+static atomic_t next_card_num = ATOMIC_INIT(1);
+
 /*******************************************************
   * SysFS Attributes
   ******************************************************/
@@ -202,7 +205,6 @@ int  kp2000_pcie_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 {
     int err = 0;
     struct kp2000_device *pcard;
-    static int card_count = 1;
     int rv;
     unsigned long reg_bar_phys_addr;
     unsigned long reg_bar_phys_len;
@@ -222,8 +224,7 @@ int  kp2000_pcie_probe(struct pci_dev *pdev, const struct pci_device_id *id)
     //}
 
     //{ Step 2: Initialize trivial pcard elements
-    pcard->card_num = card_count;
-    card_count++;
+    pcard->card_num = atomic_fetch_add(1, &next_card_num);
     scnprintf(pcard->name, 16, "kpcard%d", pcard->card_num);
 
     mutex_init(&pcard->sem);
-- 
2.20.1



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