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Re: [Xen-devel] [PATCH for-4.10] common/spinlock: Improve the output from check_lock() if it trips



Hi Andrew,

On 31/10/17 10:49, Andrew Cooper wrote:
If check_lock() triggers, a crash will occur.  Instead of simply identifying
"the irq context was different", indicate the expected and current irq
context.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Release-acked-by: Julien Grall <julien.grall@xxxxxxxxxx>

Cheers,

---
CC: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>

check_lock() only exists in debug builds, which makes this a low risk change
for 4.10.
---
  xen/common/spinlock.c | 8 +++++++-
  1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/xen/common/spinlock.c b/xen/common/spinlock.c
index 44b07b7..8f2ba08 100644
--- a/xen/common/spinlock.c
+++ b/xen/common/spinlock.c
@@ -44,7 +44,13 @@ static void check_lock(struct lock_debug *debug)
      if ( unlikely(debug->irq_safe != irq_safe) )
      {
          int seen = cmpxchg(&debug->irq_safe, -1, irq_safe);
-        BUG_ON(seen == !irq_safe);
+
+        if ( seen == !irq_safe )
+        {
+            printk("CHECKLOCK FAILURE: prev irqsafe: %d, curr irqsafe %d\n",
+                   seen, irq_safe);
+            BUG();
+        }
      }
  }

--
Julien Grall

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