From: Matt Evans <matt@ozlabs.org>
To: sarah.a.sharp@linux.intel.com
Cc: linuxppc-dev@ozlabs.org, linux-usb@vger.kernel.org
Subject: [PATCH v2 3/5] xhci: Add rmb() between reading event validity & event data access.
Date: Mon, 28 Mar 2011 15:52:57 +1100 [thread overview]
Message-ID: <4D901429.5010807@ozlabs.org> (raw)
In-Reply-To: <61164.94.211.195.167.1301094709.squirrel@gate.crashing.org>
On weakly-ordered systems, the reading of an event's content must occur
after reading the event's validity.
Signed-off-by: Matt Evans <matt@ozlabs.org>
---
Segher, thanks for the comment; explanation added.
drivers/usb/host/xhci-ring.c | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 45f3b77..d6aa880 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2152,6 +2152,11 @@ static void xhci_handle_event(struct xhci_hcd *xhci)
}
xhci_dbg(xhci, "%s - OS owns TRB\n", __func__);
+ /*
+ * Barrier between reading the TRB_CYCLE (valid) flag above and any
+ * speculative reads of the event's flags/data below.
+ */
+ rmb();
/* FIXME: Handle more event types. */
switch ((le32_to_cpu(event->event_cmd.flags) & TRB_TYPE_BITMASK)) {
case TRB_TYPE(TRB_COMPLETION):
--
1.7.0.4
next prev parent reply other threads:[~2011-03-28 4:52 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-25 7:44 [PATCH 3/5] xhci: Add rmb() between reading event validity & event data access Matt Evans
2011-03-25 23:11 ` Segher Boessenkool
2011-03-28 4:52 ` Matt Evans [this message]
2011-03-28 22:20 ` [PATCH v2 " Sarah Sharp
2011-03-29 18:56 ` Dmitry Torokhov
2011-03-29 21:23 ` Benjamin Herrenschmidt
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