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Message-ID: <20051015070426.56781.qmail@web33314.mail.mud.yahoo.com>
Date: Sat, 15 Oct 2005 00:04:26 -0700 (PDT)
From: li nux <lnxluv@yahoo.com>
Subject: lock_kernel twice possible ?
To: linux <linux-kernel@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi,

I was going thru the NFS v3 code for SMP kernel 2.6.11
to see how an inode gets revalidated. I found that
there is a possibility that there may be an attempt to
do lock_kernel() twice.

Is this possible ? If yes then how this deadlock
condition is/can be avoided.

-lnxluv

Below is the code flow (please see ** for
lock_kernel):

nfs_revalidate_inode
 - __nfs_revalidate_inode
   - ** lock_kernel() **
   - nfs_wait_on_inode
   - Call getattr() (which is nfs3_proc_getattr()) to
     get the attributes from the server and 
     refresh the inode with the new values
   - IF the cached data is invalid for the inode
     - Writeback (If dirty) and sync the 
       inode, call nfs_wb_all
     - nfs_wb_all
       - nfs_sync_inode 
           - call nfs_wait_on_requests to wait for
             the requests associated with the pages
             to get complete
           - nfs_flush_inode
             - nfs_scan_dirty
             - nfs_flush_list
               - nfs_flush_one
                 - nfs_write_rpcsetup
                   - nfs3_proc_write_setup
                     - rpc_init_task
                     - rpc_call_setup
           - nfs_execute_write
             - ** lock_kernel() **
             - rpc_execute
             - ** unlock_kernel() **
   - ** unlock_kernel() **     


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