Messages in this thread Patch in this message | | | Date | Sun, 28 Nov 2004 20:39:43 +0300 | From | Oleg Nesterov <> | Subject | [PATCH] rcu: eliminate rcu_data.last_qsctr |
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last_qsctr is used in rcu_check_quiescent_state() exclusively. We can reset qsctr at the start of the grace period, and then just test qsctr against 0.
On top of the 'rcu: eliminate rcu_ctrlblk.lock', see http://marc.theaimsgroup.com/?l=linux-kernel&m=110156786721526
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
--- 2.6.10-rc2/include/linux/rcupdate.h~ 2004-11-27 21:32:49.000000000 +0300 +++ 2.6.10-rc2/include/linux/rcupdate.h 2004-11-28 23:15:20.510856936 +0300 @@ -88,8 +88,6 @@ struct rcu_data { /* 1) quiescent state handling : */ long quiescbatch; /* Batch # for grace period */ long qsctr; /* User-mode/idle loop etc. */ - long last_qsctr; /* value of qsctr at beginning */ - /* of rcu grace period */ int qs_pending; /* core waits for quiesc state */ /* 2) batch handling */ --- 2.6.10-rc2/kernel/rcupdate.c~ 2004-11-28 23:13:03.324712400 +0300 +++ 2.6.10-rc2/kernel/rcupdate.c 2004-11-28 23:15:20.511856784 +0300 @@ -215,9 +215,9 @@ static void rcu_check_quiescent_state(st struct rcu_state *rsp, struct rcu_data *rdp) { if (rdp->quiescbatch != rcp->cur) { - /* new grace period: record qsctr value. */ + /* new grace period: reset qsctr value. */ rdp->qs_pending = 1; - rdp->last_qsctr = rdp->qsctr; + rdp->qsctr = 0; rdp->quiescbatch = rcp->cur; return; } @@ -229,12 +229,7 @@ static void rcu_check_quiescent_state(st if (!rdp->qs_pending) return; - /* - * Races with local timer interrupt - in the worst case - * we may miss one quiescent state of that CPU. That is - * tolerable. So no need to disable interrupts. - */ - if (rdp->qsctr == rdp->last_qsctr) + if (rdp->qsctr == 0) return; rdp->qs_pending = 0; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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