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    SubjectRe: [patch] Re: setitimer lowlatency-2.2.13-A1 questions
    I installed the first patch to enable_bh yesterday a few minutes
    after I received it, it ran fine for about an hour. Then I got the
    email from Andrea with a conceptually safer patch, which I also installed.
    It ran fine all afternoon, no problems. I let it run all night
    and this morning I found my kernel trace triggered on a similar
    problem (maybe the same one). It appears that irq must have
    been disabled when enable_bh was called because it seems that the timer_bh
    did not run when it should have:

    33285.97 0.37 do_IRQ pid(189)
    33286.34 2.01 do_8259A_IRQ pid(189)
    33288.36 0.33 handle_IRQ_event pid(189)
    33288.68 5.79 timer_interrupt pid(189)
    33294.48 0.72 do_timer pid(189)
    33295.20 0.81 enable_8259A_irq pid(189)
    33296.01 0.14 do_IRQ pid(189)
    33296.15 0.20 do_bottom_half pid(189)
    33296.34 0.69 do_IRQ pid(189)
    33297.03 0.14 tcp_write_space pid(189)
    33297.17 0.20 __wake_up pid(189)
    33297.37 0.30 sock_wake_async pid(189)
    33297.68 0.39 kfree_skbmem pid(189)
    33298.07 0.99 kfree pid(189)
    33299.06 0.73 kmem_cache_free pid(189)
    33299.79 0.29 __kfree_skb pid(189)
    33300.08 0.13 sock_wfree pid(189)
    .
    . --- a few more tcp_write_space sequences
    .
    33311.52 0.14 tcp_write_space pid(189)
    33311.66 0.16 __wake_up pid(189)
    33311.82 0.27 sock_wake_async pid(189)
    33312.09 0.31 kfree_skbmem pid(189)
    33312.40 0.81 kfree pid(189)
    33313.21 1.35 kmem_cache_free pid(189)
    33314.56 0.69 del_timer pid(189)
    33315.25 0.22 __kfree_skb pid(189)
    33315.47 0.26 sock_rfree pid(189)
    33315.73 0.16 kfree_skbmem pid(189)
    33315.90 0.54 kfree pid(189)
    33316.43 1.18 kmem_cache_free pid(189)
    33317.61 2516.13 do_IRQ pid(189)
    35833.75 0.66 system_call pid(189)
    35834.41 0.62 sys_sigsuspend pid(189)
    35835.03 0.80 schedule pid(189)
    35835.82 0.44 do_bottom_half pid(189)
    35836.26 0.52 timer_bh pid(189)

    I'll try to reproduce and put in a printk to verify.
    Is it *always* unsafe to do_bottom_half in enable_bh when irq disabled
    or does that only apply to the SMP case?

    Wm


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