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Date: Mon, 2 Apr 2012 23:43:23 +0000 (UTC)
From: "Vijay (Updated) (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
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Subject: [jira] [Updated] (CASSANDRA-4111) Serializing cache can cause
 Segfault in 1.1
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     [ https://issues.apache.org/jira/browse/CASSANDRA-4111?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Vijay updated CASSANDRA-4111:
-----------------------------

    Attachment: 0001-CASSANDRA-4111.patch
    
> Serializing cache can cause Segfault in 1.1
> -------------------------------------------
>
>                 Key: CASSANDRA-4111
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4111
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 1.1.0
>            Reporter: Vijay
>            Assignee: Vijay
>             Fix For: 1.1.0
>
>         Attachments: 0001-CASSANDRA-4111.patch
>
>
> Rare but this can happen per sure, looks like this issue is after CASSANDRA-3862 hence affectes only 1.1
>         FreeableMemory old = map.get(key);
>         if (old == null)
>             return false;
>         // see if the old value matches the one we want to replace
>         FreeableMemory mem = serialize(value);
>         if (mem == null)
>             return false; // out of memory.  never mind.
>         V oldValue = deserialize(old);
>         boolean success = oldValue.equals(oldToReplace) && map.replace(key, old, mem);
>         if (success)
>             old.unreference();
>         else
>             mem.unreference();
>         return success;
> in the above code block we deserialize(old) without taking reference to the old memory, this can case seg faults when the old is reclaimed (free is called)
> Fix is to get the reference just for deserialization
>         V oldValue;
>         // reference old guy before de-serializing
>         old.reference();
>         try
>         {
>              oldValue = deserialize(old);
>         }
>         finally
>         {
>             old.unreference();
>         }

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