[TG3]: Eliminate all hw IRQ handler spinlocks.

Move all driver spinlocks to be taken at sw IRQ
context only.

This fixes the skb_copy() we were doing with hw
IRQs disabled (which is illegal and triggers a
BUG() with HIGHMEM enabled).  It also simplifies
the locking all over the driver tremendously.

We accomplish this feat by creating a special
sequence to synchronize with the hw IRQ handler
using a binary state and synchronize_irq().
This idea is from Herbert Xu.

Thanks to Michael Chan for helping to track down
all of the race conditions in initial versions
of this code.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 19 insertions, 5 deletions

diff --git a/drivers/net/tg3.h b/drivers/net/tg3.h
index 993f84c93dc4..99c5f9675a56 100644
--- a/drivers/net/tg3.h
+++ b/drivers/net/tg3.h
@@ -2006,17 +2006,31 @@ struct tg3_ethtool_stats {
 struct tg3 {
         /* begin "general, frequently-used members" cacheline section */
 
+        /* If the IRQ handler (which runs lockless) needs to be
+         * quiesced, the following bitmask state is used.  The
+         * SYNC flag is set by non-IRQ context code to initiate
+         * the quiescence.
+         *
+         * When the IRQ handler notices that SYNC is set, it
+         * disables interrupts and returns.
+         *
+         * When all outstanding IRQ handlers have returned after
+         * the SYNC flag has been set, the setter can be assured
+         * that interrupts will no longer get run.
+         *
+         * In this way all SMP driver locks are never acquired
+         * in hw IRQ context, only sw IRQ context or lower.
+         */
+        unsigned int                    irq_sync;
+
         /* SMP locking strategy:
          *
          * lock: Held during all operations except TX packet
          *       processing.
          *
-         * tx_lock: Held during tg3_start_xmit{,_4gbug} and tg3_tx
+         * tx_lock: Held during tg3_start_xmit and tg3_tx
          *
-         * If you want to shut up all asynchronous processing you must
-         * acquire both locks, 'lock' taken before 'tx_lock'.  IRQs must
-         * be disabled to take 'lock' but only softirq disabling is
-         * necessary for acquisition of 'tx_lock'.
+         * Both of these locks are to be held with BH safety.
          */
         spinlock_t                      lock;
         spinlock_t                      indirect_lock;