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From: bugzilla-daemon@bugs.ecos.sourceware.org
To: ecos-bugs@ecos.sourceware.org
Subject: [Bug 1001591] New: Bogus pseudo-randomness in garbage collect
Date: Mon, 21 May 2012 13:02:00 -0000	[thread overview]
Message-ID: <bug-1001591-13@http.bugs.ecos.sourceware.org/> (raw)

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           Summary: Bogus pseudo-randomness in garbage collect
           Product: eCos
           Version: CVS
          Platform: All
        OS/Version: All
            Status: UNCONFIRMED
          Severity: major
          Priority: low
         Component: Filesystem support
        AssignedTo: unassigned@bugs.ecos.sourceware.org
        ReportedBy: stano@meduna.org
                CC: ecos-bugs@ecos.sourceware.org
             Class: Advice Request


The jffs2_find_gc_block function in fs/jffs2/current/src/gc.c and
jffs2_mark_node_obsolete in nodemgmt.c try to do pseudo-random stuff by
computing jiffies % 128 and making probability decisions on the result. First I
think that this kind of pseudo-randomness is not really correct for embedded
systems that often have very predictable execution times. 

But what is much worse, compat/linux/current/include/linux/kernel.h defines
jiffies as
  #define jiffies 100

I am no expert at jffs2 and cannot say whether this can lead to major problems
or not, so I'd like someone with better understanding of jffs2 to look at it.

Also check other usage of jiffies - I found one more in
io/usb/eth/slave/current/host/ecos_usbeth.c

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             reply	other threads:[~2012-05-21 13:02 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-21 13:02 bugzilla-daemon [this message]
2012-05-21 13:02 ` [Bug 1001591] Bogus pseudo-randomness in jffs2 " bugzilla-daemon
2012-05-26 15:46 ` bugzilla-daemon
2012-05-27  0:53 ` bugzilla-daemon
2012-05-27  0:53 ` bugzilla-daemon
2012-05-21 13:02 [Bug 1001591] New: Bogus pseudo-randomness in " bugzilla-daemon

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