[xen staging] lockprof: don't leave locks uninitialized upon allocation failure

[patchbot@xxxxxxx]

commit 82cba984b2e37496360ef2bf22e529a53c084631
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Jul 24 10:18:30 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Jul 24 10:18:30 2020 +0200

    lockprof: don't leave locks uninitialized upon allocation failure
    
    Even if a specific struct lock_profile instance can't be allocated, the
    lock itself should still be functional. As this isn't a production use
    feature, also log a message in the event that the profiling struct can't
    be allocated.
    
    Fixes: d98feda5c756 ("Make lock profiling usable again")
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/include/xen/spinlock.h | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/xen/include/xen/spinlock.h b/xen/include/xen/spinlock.h
index 468b9ac9ef..c0e7690a6c 100644
--- a/xen/include/xen/spinlock.h
+++ b/xen/include/xen/spinlock.h
@@ -103,10 +103,16 @@ struct lock_profile_qhead {
     do {                                                                      \
         struct lock_profile *prof;                                            \
         prof = xzalloc(struct lock_profile);                                  \
-        if (!prof) break;                                                     \
+        (s)->l = (spinlock_t)_SPIN_LOCK_UNLOCKED(prof);                       \
+        if ( !prof )                                                          \
+        {                                                                     \
+            printk(XENLOG_WARNING                                             \
+                   "lock profiling unavailable for %p(%d)'s %s\n",            \
+                   s, (s)->profile_head.idx, #l);                             \
+            break;                                                            \
+        }                                                                     \
         prof->name = #l;                                                      \
         prof->lock = &(s)->l;                                                 \
-        (s)->l = (spinlock_t)_SPIN_LOCK_UNLOCKED(prof);                       \
         prof->next = (s)->profile_head.elem_q;                                \
         (s)->profile_head.elem_q = prof;                                      \
     } while(0)
--
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