ipq40xx: essedma: Fix dead lock

edma_read_append_stats() gets called from two places in the driver.
The first place is the kernel timer that periodically updates
the statistics, so nothing gets lost due to overflows.
The second one it's part of the userspace ethtool ioctl handler
to provide up-to-date values.

For this configuration, the use of spin_lock() is not sufficient
and as per:
<https://mirrors.edge.kernel.org/pub/linux/kernel/people/rusty/kernel-locking/c214.html>
the locking has to be upgraded to spin_lock_bh().

Signed-off-by: Masafumi UTSUGI <mutsugi@allied-telesis.co.jp>
[folded patch into 710-, rewrote message]
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
(cherry picked from commit f1d761f95e9664a9c11ce1b98f9e121b43c79d35)

diff --git a/target/linux/ipq40xx/patches-4.14/710-net-add-qualcomm-essedma-ethernet-driver.patch b/target/linux/ipq40xx/patches-4.14/710-net-add-qualcomm-essedma-ethernet-driver.patch
index e304911f1d8fa91fe83a370b3c91c91bd98659e4..1e47f2fe90af0d01460414eb38d7f39b11753ce8 100644 (file)
--- a/target/linux/ipq40xx/patches-4.14/710-net-add-qualcomm-essedma-ethernet-driver.patch
+++ b/target/linux/ipq40xx/patches-4.14/710-net-add-qualcomm-essedma-ethernet-driver.patch
@@ -2775,7 +2775,7 @@ Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
 +      int i;
 +      u32 stat;
 +
-+      spin_lock(&edma_cinfo->stats_lock);
++      spin_lock_bh(&edma_cinfo->stats_lock);
 +      p = (uint32_t *)&(edma_cinfo->edma_ethstats);
 +
 +      for (i = 0; i < EDMA_MAX_TRANSMIT_QUEUE; i++) {
@@ -2802,7 +2802,7 @@ Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
 +              p++;
 +      }
 +
-+      spin_unlock(&edma_cinfo->stats_lock);
++      spin_unlock_bh(&edma_cinfo->stats_lock);
 +}
 +
 +static void edma_statistics_timer(unsigned long data)