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| Started by | "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> |
|---|---|
| First post | 2016-04-12 17:20 +0200 |
| Last post | 2016-04-12 17:20 +0200 |
| Articles | 1 — 1 participant |
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[PATCH tip/core/rcu 08/10] documentation: Sharpen up the no-readers quick quiz "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-04-12 17:20 +0200
| From | "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> |
|---|---|
| Date | 2016-04-12 17:20 +0200 |
| Subject | [PATCH tip/core/rcu 08/10] documentation: Sharpen up the no-readers quick quiz |
| Message-ID | <rn8gF-10N-9@gated-at.bofh.it> |
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> --- Documentation/RCU/Design/Requirements/Requirements.html | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html index acdad96f78e9..85cf2238fd08 100644 --- a/Documentation/RCU/Design/Requirements/Requirements.html +++ b/Documentation/RCU/Design/Requirements/Requirements.html @@ -1002,18 +1002,21 @@ obligation to wait for these new readers. <tr><th> </th></tr> <tr><th align="left">Quick Quiz:</th></tr> <tr><td> - Suppose that synchronize_rcu() did wait until all readers had completed. - Would the updater be able to rely on this? + Suppose that synchronize_rcu() did wait until <i>all</i> + readers had completed instead of waiting only on + pre-existing readers. + For how long would the updater be able to rely on there + being no readers? </td></tr> <tr><th align="left">Answer:</th></tr> <tr><td bgcolor="#ffffff"><font color="ffffff"> - No. + For no time at all. Even if <tt>synchronize_rcu()</tt> were to wait until all readers had completed, a new reader might start immediately after <tt>synchronize_rcu()</tt> completed. Therefore, the code following - <tt>synchronize_rcu()</tt> cannot rely on there being no readers - in any case. + <tt>synchronize_rcu()</tt> can <i>never</i> rely on there being + no readers. </font></td></tr> <tr><td> </td></tr> </table> -- 2.5.2
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