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Message-ID: <20230710192440.47140-3-ubizjak@gmail.com>
Date: Mon, 10 Jul 2023 21:21:56 +0200
From: Uros Bizjak <ubizjak@...il.com>
To: linux-kernel@...r.kernel.org, x86@...nel.org,
xen-devel@...ts.xenproject.org
Cc: Uros Bizjak <ubizjak@...il.com>,
Peter Zijlstra <peterz@...radead.org>,
Juergen Gross <jgross@...e.com>,
Stefano Stabellini <sstabellini@...nel.org>,
Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
Subject: [PATCH 3/3] xen: Illustrate the transition to sync_try_cmpxchg
This patch illustrates the transition to sync_try_cmpxchg.
It is not intended to be merged as-is.
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Juergen Gross <jgross@...e.com>
Cc: Stefano Stabellini <sstabellini@...nel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
Signed-off-by: Uros Bizjak <ubizjak@...il.com>
---
drivers/xen/events/events_fifo.c | 26 ++++++++++++--------------
drivers/xen/grant-table.c | 10 ++++------
2 files changed, 16 insertions(+), 20 deletions(-)
diff --git a/drivers/xen/events/events_fifo.c b/drivers/xen/events/events_fifo.c
index ad9fe51d3fb3..655775db7caf 100644
--- a/drivers/xen/events/events_fifo.c
+++ b/drivers/xen/events/events_fifo.c
@@ -226,21 +226,20 @@ static bool evtchn_fifo_is_masked(evtchn_port_t port)
*/
static bool clear_masked_cond(volatile event_word_t *word)
{
- event_word_t new, old, w;
+ event_word_t new, old;
- w = *word;
+ old = *word;
do {
- if (!(w & (1 << EVTCHN_FIFO_MASKED)))
+ if (!(old & (1 << EVTCHN_FIFO_MASKED)))
return true;
- if (w & (1 << EVTCHN_FIFO_PENDING))
+ if (old & (1 << EVTCHN_FIFO_PENDING))
return false;
- old = w & ~(1 << EVTCHN_FIFO_BUSY);
+ old = old & ~(1 << EVTCHN_FIFO_BUSY);
new = old & ~(1 << EVTCHN_FIFO_MASKED);
- w = sync_cmpxchg(word, old, new);
- } while (w != old);
+ } while (!sync_try_cmpxchg(word, &old, new));
return true;
}
@@ -259,17 +258,16 @@ static void evtchn_fifo_unmask(evtchn_port_t port)
static uint32_t clear_linked(volatile event_word_t *word)
{
- event_word_t new, old, w;
+ event_word_t new, old;
- w = *word;
+ old = *word;
do {
- old = w;
- new = (w & ~((1 << EVTCHN_FIFO_LINKED)
- | EVTCHN_FIFO_LINK_MASK));
- } while ((w = sync_cmpxchg(word, old, new)) != old);
+ new = (old & ~((1 << EVTCHN_FIFO_LINKED)
+ | EVTCHN_FIFO_LINK_MASK));
+ } while (!sync_try_cmpxchg(word, &old, new));
- return w & EVTCHN_FIFO_LINK_MASK;
+ return old & EVTCHN_FIFO_LINK_MASK;
}
static void consume_one_event(unsigned cpu, struct evtchn_loop_ctrl *ctrl,
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index e1ec725c2819..211d083d4fbe 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -427,16 +427,14 @@ EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);
static int gnttab_end_foreign_access_ref_v1(grant_ref_t ref)
{
- u16 flags, nflags;
- u16 *pflags;
+ u16 *pflags = &gnttab_shared.v1[ref].flags;
+ u16 flags;
- pflags = &gnttab_shared.v1[ref].flags;
- nflags = *pflags;
+ flags = *pflags;
do {
- flags = nflags;
if (flags & (GTF_reading|GTF_writing))
return 0;
- } while ((nflags = sync_cmpxchg(pflags, flags, 0)) != flags);
+ } while (!sync_try_cmpxchg(pflags, &flags, 0));
return 1;
}
--
2.41.0
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