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[Xen-devel] [PATCH] Xentrace: Avoid Crash on Debug Build Xen



Mark Williamson wrote:
         }
         total_size += LOST_REC_SIZE;
     }
-
-    ASSERT(bytes_to_wrap == calc_bytes_to_wrap(buf));
if ( rec_size > bytes_to_wrap )
     {
@@ -484,8 +482,6 @@ void __trace_var(u32 event, int cycles, insert_lost_records(buf);
     }
- ASSERT(bytes_to_wrap == calc_bytes_to_wrap(buf));
-

Current xen-unstable (debug build) crashes when using xentrace command,
due to assertion failures. It seems assertion failures occur whenever
there exist lost records, and I don't see much reason to do this.
(Could anyone explain about these ASSERT lines ?)

These asserts appear to have originally been checking that bytes_to_wrap is being calculated correctly... It looks to me that the first assert isoutdated though, because it clearly will fail if a record is lost.

Perhaps the second one ought to succed though, since the value of buf->prod will have been appropriately updated by insert_lost_records()?

Indeed the second assert seems to always succeed.


Cheers,
Mark

The attached patch removes assertions to avoid system crashes,
and also fixes a mistake of an assignment statement.

Regards,
-------------------
Yosuke Iwamatsu
        NEC Corporation






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