diff options
Diffstat (limited to 'Documentation/RCU')
| -rw-r--r-- | Documentation/RCU/Design/Requirements/Requirements.html | 35 | ||||
| -rw-r--r-- | Documentation/RCU/stallwarn.txt | 2 | ||||
| -rw-r--r-- | Documentation/RCU/whatisRCU.txt | 3 |
3 files changed, 39 insertions, 1 deletions
diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html index e7e24b3e8..ece410f40 100644 --- a/Documentation/RCU/Design/Requirements/Requirements.html +++ b/Documentation/RCU/Design/Requirements/Requirements.html @@ -2391,6 +2391,41 @@ and <tt>RCU_NONIDLE()</tt> on the other while inspecting idle-loop code. Steven Rostedt supplied <tt>_rcuidle</tt> event tracing, which is used quite heavily in the idle loop. +However, there are some restrictions on the code placed within +<tt>RCU_NONIDLE()</tt>: + +<ol> +<li> Blocking is prohibited. + In practice, this is not a serious restriction given that idle + tasks are prohibited from blocking to begin with. +<li> Although nesting <tt>RCU_NONIDLE()</tt> is permited, they cannot + nest indefinitely deeply. + However, given that they can be nested on the order of a million + deep, even on 32-bit systems, this should not be a serious + restriction. + This nesting limit would probably be reached long after the + compiler OOMed or the stack overflowed. +<li> Any code path that enters <tt>RCU_NONIDLE()</tt> must sequence + out of that same <tt>RCU_NONIDLE()</tt>. + For example, the following is grossly illegal: + + <blockquote> + <pre> + 1 RCU_NONIDLE({ + 2 do_something(); + 3 goto bad_idea; /* BUG!!! */ + 4 do_something_else();}); + 5 bad_idea: + </pre> + </blockquote> + + <p> + It is just as illegal to transfer control into the middle of + <tt>RCU_NONIDLE()</tt>'s argument. + Yes, in theory, you could transfer in as long as you also + transferred out, but in practice you could also expect to get sharply + worded review comments. +</ol> <p> It is similarly socially unacceptable to interrupt an diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt index 0f7fb4298..e93d04133 100644 --- a/Documentation/RCU/stallwarn.txt +++ b/Documentation/RCU/stallwarn.txt @@ -49,7 +49,7 @@ rcupdate.rcu_task_stall_timeout This boot/sysfs parameter controls the RCU-tasks stall warning interval. A value of zero or less suppresses RCU-tasks stall warnings. A positive value sets the stall-warning interval - in jiffies. An RCU-tasks stall warning starts wtih the line: + in jiffies. An RCU-tasks stall warning starts with the line: INFO: rcu_tasks detected stalls on tasks: diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt index 111770ffa..204422719 100644 --- a/Documentation/RCU/whatisRCU.txt +++ b/Documentation/RCU/whatisRCU.txt @@ -5,6 +5,9 @@ to start learning about RCU: 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/ 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/ 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/ + 2010 Big API Table http://lwn.net/Articles/419086/ +5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/ + 2014 Big API Table http://lwn.net/Articles/609973/ What is RCU? |