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    SubjectRe: [RFC PATCH 07/12] e1000e: debug contention on NVM SWFLAG
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    On Thursday 02 October 2008 16:28:42 Jiri Kosina wrote:
    >
    > 15:50:52 linux-pr0e kernel: WARNING: at drivers/net/e1000e/ich8lan.c:424 e1000_acquire_swflag_ich8lan+0x5a/0xdc [e1000e]()
    > 15:50:52 linux-pr0e kernel: e1000e mutex contention. Owned by pid 4162
    > 15:50:52 linux-pr0e kernel: Call Trace:
    > 15:50:52 linux-pr0e kernel: [<ffffffff8020e41e>] show_trace_log_lvl+0x41/0x58
    > 15:50:52 linux-pr0e kernel: [<ffffffff80493716>] dump_stack+0x69/0x6f
    > 15:50:52 linux-pr0e kernel: [<ffffffff8023ee54>] warn_slowpath+0xb4/0xdc
    > 15:50:52 linux-pr0e kernel: [<ffffffffa022ce2e>] e1000_acquire_swflag_ich8lan+0x5a/0xdc [e1000e]
    > 15:50:52 linux-pr0e kernel: [<ffffffffa02317ba>] e1000e_read_phy_reg_igp+0x19/0x64 [e1000e]
    > 15:50:52 linux-pr0e kernel: [<ffffffffa02319f8>] e1000e_phy_has_link_generic+0x50/0xcc [e1000e]
    > 15:50:52 linux-pr0e kernel: [<ffffffffa02306f9>] e1000e_check_for_copper_link+0x24/0x86 [e1000e]
    > 15:50:52 linux-pr0e kernel: [<ffffffffa0236982>] e1000_watchdog_task+0x5c/0x5eb [e1000e]
    > 15:50:52 linux-pr0e kernel: [<ffffffff8024ecdb>] run_workqueue+0xa4/0x14c
    > 15:50:52 linux-pr0e kernel: [<ffffffff8024ee5b>] worker_thread+0xd8/0xe7
    > 15:50:52 linux-pr0e kernel: [<ffffffff80251fe5>] kthread+0x47/0x73
    > 15:50:52 linux-pr0e kernel: [<ffffffff8020d7a9>] child_rip+0xa/0x11

    Looks like the e1000 watchdog racing with some dhclient activity (upping the interface).

    I just noticed that the driver actually uses register pages. So it looks like it's
    possible to have something like this without the mutex:

    process A selects page A
    process B selects page B
    process A writes to register at offset A'

    So we may end up writing to the wrong register. I think I heard Vojtech mention
    that the e1000e also has a register based interface to erase/rewrite the NVM
    programmatically. Do we know at which offsets these registers live?

    Olaf
    --
    Neo didn't bring down the Matrix. SOA did.
    --soafacts.com



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