Attachment 575160 Details for Bug 806548 – git bisect visualize

git bisect visualize

bad_commit.txt (text/plain), 1.47 KB, created by Pascal Chapperon on 2012-04-04 14:51:04 UTC

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Creator: Pascal Chapperon

Created: 2012-04-04 14:51:04 UTC

Size: 1.47 KB

patch

obsolete

>commit 7cb92499000e3c86dae653077b1465458a039ef6
>Author: Paul E. McKenney <paul.mckenney@linaro.org>
>Date:   Mon Nov 28 12:28:34 2011 -0800
>
>    rcu: Permit dyntick-idle with callbacks pending
>    
>    The current implementation of RCU_FAST_NO_HZ prevents CPUs from entering
>    dyntick-idle state if they have RCU callbacks pending.  Unfortunately,
>    this has the side-effect of often preventing them from entering this
>    state, especially if at least one other CPU is not in dyntick-idle state.
>    However, the resulting per-tick wakeup is wasteful in many cases: if the
>    CPU has already fully responded to the current RCU grace period, there
>    will be nothing for it to do until this grace period ends, which will
>    frequently take several jiffies.
>    
>    This commit therefore permits a CPU that has done everything that the
>    current grace period has asked of it (rcu_pending() == 0) even if it
>    still as RCU callbacks pending.  However, such a CPU posts a timer to
>    wake it up several jiffies later (6 jiffies, based on experience with
>    grace-period lengths).  This wakeup is required to handle situations
>    that can result in all CPUs being in dyntick-idle mode, thus failing
>    to ever complete the current grace period.  If a CPU wakes up before
>    the timer goes off, then it cancels that timer, thus avoiding spurious
>    wakeups.
>    
>    Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
>    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

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Attachments on bug 806548: 572829 | 572836 | 572837 | 572847 | 572850 | 574324 | 574326 | 575157 | 575160 | 575381 | 579003 | 579125 | 579161 | 579162 | 580740