This race conditions occurs with reentrant e1000_down(), which gets
called by multiple threads while driver unload or reset.
This patch fixes the race condition when one thread tries to destroy
the memory allocated for tx buffer_info, while another thread still
happen to access tx buffer_info.
This patch fixes the above race condition using kref count.
Signed-off-by: Prasanna S. Panchamukhi <prasanna.panchamu...@riverbed.com>
---
drivers/net/e1000/e1000.h | 2 +
drivers/net/e1000/e1000_main.c | 41 +++++++++++++++++++++++++++++++++++++--
2 files changed, 40 insertions(+), 3 deletions(-)
diff --git a/drivers/net/e1000/e1000.h b/drivers/net/e1000/e1000.h
index a881dd0..36f55b3 100644
--- a/drivers/net/e1000/e1000.h
+++ b/drivers/net/e1000/e1000.h
@@ -168,6 +168,8 @@ struct e1000_tx_ring {
unsigned int next_to_clean;
/* array of buffer information structs */
struct e1000_buffer *buffer_info;
+ spinlock_t bufinfo_lock; /* protect access to buffer_info */
+ struct kref bufinfo_refcount; /* refcount access to buffer info */
u16 tdh;
u16 tdt;
diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c
index beec573..336d3e1 100644
--- a/drivers/net/e1000/e1000_main.c
+++ b/drivers/net/e1000/e1000_main.c
@@ -1531,6 +1531,8 @@ setup_tx_desc_die:
txdr->next_to_use = 0;
txdr->next_to_clean = 0;
+ spin_lock_init(&txdr->bufinfo_lock);
+ kref_init(&txdr->bufinfo_refcount);
return 0;
}
@@ -1880,6 +1882,22 @@ static void e1000_configure_rx(struct e1000_adapter
*adapter)
ew32(RCTL, rctl);
}
+/*
+ * Free tx buffer info resources, only when no other thread is
+ * accessing it. Access to buffer_info is refcounted by bufinfo_refcount,
+ * hence memory allocated must be destroyed when bufinfo_refcount
+ * becomes zero. This routine gets executed when bufinfo_refcount
+ * becomes zero.
+ */
+static void e1000_free_tx_buffer_info(struct kref *ref)
+{
+ struct e1000_tx_ring *tx_ring =
+ container_of(ref, struct e1000_tx_ring, bufinfo_refcount);
+
+ vfree(tx_ring->buffer_info);
+ tx_ring->buffer_info = NULL;
+}
+
/**
* e1000_free_tx_resources - Free Tx Resources per Queue
* @adapter: board private structure
@@ -1895,8 +1913,9 @@ static void e1000_free_tx_resources(struct e1000_adapter
*adapter,
e1000_clean_tx_ring(adapter, tx_ring);
- vfree(tx_ring->buffer_info);
- tx_ring->buffer_info = NULL;
+ spin_lock(&tx_ring->bufinfo_lock);
+ kref_put(&tx_ring->bufinfo_refcount, e1000_free_tx_buffer_info);
+ spin_unlock(&tx_ring->bufinfo_lock);
dma_free_coherent(&pdev->dev, tx_ring->size, tx_ring->desc,
tx_ring->dma);
@@ -1954,8 +1973,20 @@ static void e1000_clean_tx_ring(struct e1000_adapter
*adapter,
unsigned long size;
unsigned int i;
- /* Free all the Tx ring sk_buffs */
+ spin_lock(&tx_ring->bufinfo_lock);
+ /*
+ * Check buffer_info is not NULL, and
+ * increment the refcount to prevent
+ * the buffer getting freed underneath.
+ */
+ if (tx_ring->buffer_info == NULL) {
+ spin_unlock(&tx_ring->bufinfo_lock);
+ return;
+ }
+ kref_get(&tx_ring->bufinfo_refcount);
+ spin_unlock(&tx_ring->bufinfo_lock);
+ /* Free all the Tx ring sk_buffs */
for (i = 0; i < tx_ring->count; i++) {
buffer_info = &tx_ring->buffer_info[i];
e1000_unmap_and_free_tx_resource(adapter, buffer_info);
@@ -1968,6 +1999,10 @@ static void e1000_clean_tx_ring(struct e1000_adapter
*adapter,
memset(tx_ring->desc, 0, tx_ring->size);
+ spin_lock(&tx_ring->bufinfo_lock);
+ kref_put(&tx_ring->bufinfo_refcount, e1000_free_tx_buffer_info);
+ spin_unlock(&tx_ring->bufinfo_lock);
+
tx_ring->next_to_use = 0;
tx_ring->next_to_clean = 0;
tx_ring->last_tx_tso = 0;
--
1.7.0.4
------------------------------------------------------------------------------
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