Messages in this thread | | | Date | Sat, 20 Jan 2018 01:00:12 +0100 | From | Francois Romieu <> | Subject | Re: net: r8169: a question of memory barrier in the r8169 driver |
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Peter Zijlstra <peterz@infradead.org> : > On Fri, Jan 19, 2018 at 02:11:18AM +0100, Francois Romieu wrote: > > Peter Zijlstra <peterz@infradead.org> : > > [...] > > > There is only 1 variable afaict. Memory barriers need at least 2 in > > > order to be able to do _anything_. > > > > I don't get your point: why don't {cur_tx, dirty_tx} qualify as said > > two variables ? > > There wasn't any cur_tx in the code you provided.
/* A skbuff with nr_frags needs nr_frags+1 entries in the tx queue */ #define TX_FRAGS_READY_FOR(tp,nr_frags) \ (TX_SLOTS_AVAIL(tp) >= (nr_frags + 1))
#define TX_SLOTS_AVAIL(tp) \ (tp->dirty_tx + NUM_TX_DESC - tp->cur_tx)
Both are also used in rtl_tx.
I don't get your point. Even a single variable is scattered through the system.
-- Ueimor
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