[BUG] net: tg3: two possible data races

The call paths in Linux 4.16.7 that may raise the first data race:

CPU0:
tg3_open
     tg3_start
         line 11611: spin_lock_bh()
         tg3_enable_ints
             line 1023: tp->tnapi->last_tag [READ]

CPU1:
tg3_poll
     line 7341: tnapi->last_tag [WRITE]

The READ operation in CPU0 is performed with holding a spinlock (line 
11611), but the WRITE operation in CPU1 is performed without holding 
this spinlock, so it may cause a data race here.
A possible fix may be to add spin_lock_bh() in tg3_poll().

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The call paths in Linux 4.16.7 that may raise the second data race:

CPU0:
tg3_open
     tg3_start
         line 11611: spin_lock_bh()
         tg3_enable_ints
             line 1023: tp->irq_sync [WRITE]

CPU1:
tg3_interrupt_tagged
     tg3_irq_sync
         line 7341: tp->irq_sync [READ]

The WRITE operation in CPU0 is performed with holding a spinlock (line 
11611), but the READ operation in CPU1 is performed without holding this 
spinlock, so it may cause a data race here.
A possible fix may be to add spin_lock_bh() in tg3_irq_sync().

I am not sure that whether the possible fixes are correct, so I only 
report the data races.


Best wishes,
Jia-Ju Bai