linux-kernel - Re: next-20090310: ext4 hangs

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Message-ID: <20090326000035.GB11024@duck.suse.cz>
Date:	Thu, 26 Mar 2009 01:00:36 +0100
From:	Jan Kara <jack@...e.cz>
To:	Alexander Beregalov <a.beregalov@...il.com>
Cc:	Theodore Tso <tytso@....edu>,
	"linux-next@...r.kernel.org" <linux-next@...r.kernel.org>,
	linux-ext4@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	sparclinux@...r.kernel.org
Subject: Re: next-20090310: ext4 hangs

  Hi,

  thanks for the updated disassembly.

>   55bab0:       82 10 60 01     or  %g1, 1, %g1
>                 spin_unlock(&journal->j_list_lock);
>   55bab4:       40 06 4b 20     call  6ee734 <_spin_unlock>
>   55bab8:       c2 24 e0 28     st  %g1, [ %l3 + 0x28 ]
  OK, so it really seems that:
  jinode->i_flags |= JI_COMMIT_RUNNING;
  spin_unlock(&journal->j_list_lock);

  has been compiled to
  ld [ %l3 + 0x28 ], %g1
  or  %g1, 1, %g1
  call  6ee734 <_spin_unlock>
  st  %g1, [ %l3 + 0x28 ]

  Which seems like a bug in the compiler or in the way implement compiler
barriers in spin_unlock() on UP sparc. Or is there some sparc magic by which
this is correct code? Any clever sparc guy?

									Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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