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author | Linus Torvalds <torvalds@linux-foundation.org> | 2016-07-25 12:04:11 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-07-25 12:04:11 -0700 |
commit | df00ccca7201dcb78847de68538486dbcfa5deba (patch) | |
tree | 2e572a32d6d19e9be5736b82a62f4c23f6eac2d3 /Documentation | |
parent | dd9506954539dcedd0294a065ff0976e61386fc6 (diff) | |
parent | 54d5f16e55a7cdd64e0f6bcadf2b5f871f94bb83 (diff) | |
download | linux-df00ccca7201dcb78847de68538486dbcfa5deba.tar.gz linux-df00ccca7201dcb78847de68538486dbcfa5deba.tar.bz2 linux-df00ccca7201dcb78847de68538486dbcfa5deba.zip |
Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU updates from Ingo Molnar:
"The main changes in this cycle were:
- documentation updates
- miscellaneous fixes
- minor reorganization of code
- torture-test updates"
* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (30 commits)
rcu: Correctly handle sparse possible cpus
rcu: sysctl: Panic on RCU Stall
rcu: Fix a typo in a comment
rcu: Make call_rcu_tasks() tolerate first call with irqs disabled
rcu: Disable TASKS_RCU for usermode Linux
rcu: No ordering for rcu_assign_pointer() of NULL
rcutorture: Fix error return code in rcu_perf_init()
torture: Inflict default jitter
rcuperf: Don't treat gp_exp mis-setting as a WARN
rcutorture: Drop "-soundhw pcspkr" from x86 boot arguments
rcutorture: Don't specify the cpu type of QEMU on PPC
rcutorture: Make -soundhw a x86 specific option
rcutorture: Use vmlinux as the fallback kernel image
rcutorture/doc: Create initrd using dracut
torture: Stop onoff task if there is only one cpu
torture: Add starvation events to error summary
torture: Break online and offline functions out of torture_onoff()
torture: Forgive lengthy trace dumps and preemption
torture: Remove CONFIG_RCU_TORTURE_TEST_RUNNABLE, simplify code
torture: Simplify code, eliminate RCU_PERF_TEST_RUNNABLE
...
Diffstat (limited to 'Documentation')
-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 | ||||
-rw-r--r-- | Documentation/sysctl/kernel.txt | 12 |
4 files changed, 51 insertions, 1 deletions
diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html index e7e24b3e86e2..ece410f40436 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 0f7fb4298e7e..e93d04133fe7 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 111770ffa10e..204422719197 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? diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index a3683ce2a2f3..33204604de6c 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -58,6 +58,7 @@ show up in /proc/sys/kernel: - panic_on_stackoverflow - panic_on_unrecovered_nmi - panic_on_warn +- panic_on_rcu_stall - perf_cpu_time_max_percent - perf_event_paranoid - perf_event_max_stack @@ -618,6 +619,17 @@ a kernel rebuild when attempting to kdump at the location of a WARN(). ============================================================== +panic_on_rcu_stall: + +When set to 1, calls panic() after RCU stall detection messages. This +is useful to define the root cause of RCU stalls using a vmcore. + +0: do not panic() when RCU stall takes place, default behavior. + +1: panic() after printing RCU stall messages. + +============================================================== + perf_cpu_time_max_percent: Hints to the kernel how much CPU time it should be allowed to |