From 99f88919f8fa8a8b01b5306c59c9977b94604df8 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 12 Mar 2013 16:54:14 -0700 Subject: rcu: Remove srcu_read_lock_raw() and srcu_read_unlock_raw(). These interfaces never did get used, so this commit removes them, their rcutorture tests, and documentation referencing them. Signed-off-by: Paul E. McKenney Reviewed-by: Lai Jiangshan Reviewed-by: Josh Triplett --- Documentation/RCU/checklist.txt | 6 ------ Documentation/RCU/torture.txt | 6 ------ Documentation/RCU/whatisRCU.txt | 22 +++++++--------------- 3 files changed, 7 insertions(+), 27 deletions(-) (limited to 'Documentation/RCU') diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt index 79e789b8..7703ec7 100644 --- a/Documentation/RCU/checklist.txt +++ b/Documentation/RCU/checklist.txt @@ -354,12 +354,6 @@ over a rather long period of time, but improvements are always welcome! using RCU rather than SRCU, because RCU is almost always faster and easier to use than is SRCU. - If you need to enter your read-side critical section in a - hardirq or exception handler, and then exit that same read-side - critical section in the task that was interrupted, then you need - to srcu_read_lock_raw() and srcu_read_unlock_raw(), which avoid - the lockdep checking that would otherwise this practice illegal. - Also unlike other forms of RCU, explicit initialization and cleanup is required via init_srcu_struct() and cleanup_srcu_struct(). These are passed a "struct srcu_struct" diff --git a/Documentation/RCU/torture.txt b/Documentation/RCU/torture.txt index 7dce8a1..d8a5023 100644 --- a/Documentation/RCU/torture.txt +++ b/Documentation/RCU/torture.txt @@ -182,12 +182,6 @@ torture_type The type of RCU to test, with string values as follows: "srcu_expedited": srcu_read_lock(), srcu_read_unlock() and synchronize_srcu_expedited(). - "srcu_raw": srcu_read_lock_raw(), srcu_read_unlock_raw(), - and call_srcu(). - - "srcu_raw_sync": srcu_read_lock_raw(), srcu_read_unlock_raw(), - and synchronize_srcu(). - "sched": preempt_disable(), preempt_enable(), and call_rcu_sched(). diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt index 10df0b8..0f0fb7c 100644 --- a/Documentation/RCU/whatisRCU.txt +++ b/Documentation/RCU/whatisRCU.txt @@ -842,9 +842,7 @@ SRCU: Critical sections Grace period Barrier srcu_read_lock synchronize_srcu srcu_barrier srcu_read_unlock call_srcu - srcu_read_lock_raw synchronize_srcu_expedited - srcu_read_unlock_raw - srcu_dereference + srcu_dereference synchronize_srcu_expedited SRCU: Initialization/cleanup init_srcu_struct @@ -865,38 +863,32 @@ list can be helpful: a. Will readers need to block? If so, you need SRCU. -b. Is it necessary to start a read-side critical section in a - hardirq handler or exception handler, and then to complete - this read-side critical section in the task that was - interrupted? If so, you need SRCU's srcu_read_lock_raw() and - srcu_read_unlock_raw() primitives. - -c. What about the -rt patchset? If readers would need to block +b. What about the -rt patchset? If readers would need to block in an non-rt kernel, you need SRCU. If readers would block in a -rt kernel, but not in a non-rt kernel, SRCU is not necessary. -d. Do you need to treat NMI handlers, hardirq handlers, +c. Do you need to treat NMI handlers, hardirq handlers, and code segments with preemption disabled (whether via preempt_disable(), local_irq_save(), local_bh_disable(), or some other mechanism) as if they were explicit RCU readers? If so, RCU-sched is the only choice that will work for you. -e. Do you need RCU grace periods to complete even in the face +d. Do you need RCU grace periods to complete even in the face of softirq monopolization of one or more of the CPUs? For example, is your code subject to network-based denial-of-service attacks? If so, you need RCU-bh. -f. Is your workload too update-intensive for normal use of +e. Is your workload too update-intensive for normal use of RCU, but inappropriate for other synchronization mechanisms? If so, consider SLAB_DESTROY_BY_RCU. But please be careful! -g. Do you need read-side critical sections that are respected +f. Do you need read-side critical sections that are respected even though they are in the middle of the idle loop, during user-mode execution, or on an offlined CPU? If so, SRCU is the only choice that will work for you. -h. Otherwise, use RCU. +g. Otherwise, use RCU. Of course, this all assumes that you have determined that RCU is in fact the right tool for your job. -- cgit v1.1 From 7807acdb6b794b3af42dfa1912edd4fba8d0b622 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 27 Mar 2013 11:32:12 -0700 Subject: rcu: Remove TINY_PREEMPT_RCU tracing documentation Because TINY_PREEMPT_RCU is no more, this commit removes its tracing formats from the documentation. Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- Documentation/RCU/trace.txt | 100 ++------------------------------------------ 1 file changed, 4 insertions(+), 96 deletions(-) (limited to 'Documentation/RCU') diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt index c776968..f3778f8 100644 --- a/Documentation/RCU/trace.txt +++ b/Documentation/RCU/trace.txt @@ -530,113 +530,21 @@ o "nos" counts the number of times we balked for other reasons, e.g., the grace period ended first. -CONFIG_TINY_RCU and CONFIG_TINY_PREEMPT_RCU debugfs Files and Formats +CONFIG_TINY_RCU debugfs Files and Formats These implementations of RCU provides a single debugfs file under the top-level directory RCU, namely rcu/rcudata, which displays fields in -rcu_bh_ctrlblk, rcu_sched_ctrlblk and, for CONFIG_TINY_PREEMPT_RCU, -rcu_preempt_ctrlblk. +rcu_bh_ctrlblk and rcu_sched_ctrlblk. The output of "cat rcu/rcudata" is as follows: -rcu_preempt: qlen=24 gp=1097669 g197/p197/c197 tasks=... - ttb=. btg=no ntb=184 neb=0 nnb=183 j=01f7 bt=0274 - normal balk: nt=1097669 gt=0 bt=371 b=0 ny=25073378 nos=0 - exp balk: bt=0 nos=0 rcu_sched: qlen: 0 rcu_bh: qlen: 0 -This is split into rcu_preempt, rcu_sched, and rcu_bh sections, with the -rcu_preempt section appearing only in CONFIG_TINY_PREEMPT_RCU builds. -The last three lines of the rcu_preempt section appear only in -CONFIG_RCU_BOOST kernel builds. The fields are as follows: +This is split into rcu_sched and rcu_bh sections. The field is as +follows: o "qlen" is the number of RCU callbacks currently waiting either for an RCU grace period or waiting to be invoked. This is the only field present for rcu_sched and rcu_bh, due to the short-circuiting of grace period in those two cases. - -o "gp" is the number of grace periods that have completed. - -o "g197/p197/c197" displays the grace-period state, with the - "g" number being the number of grace periods that have started - (mod 256), the "p" number being the number of grace periods - that the CPU has responded to (also mod 256), and the "c" - number being the number of grace periods that have completed - (once again mode 256). - - Why have both "gp" and "g"? Because the data flowing into - "gp" is only present in a CONFIG_RCU_TRACE kernel. - -o "tasks" is a set of bits. The first bit is "T" if there are - currently tasks that have recently blocked within an RCU - read-side critical section, the second bit is "N" if any of the - aforementioned tasks are blocking the current RCU grace period, - and the third bit is "E" if any of the aforementioned tasks are - blocking the current expedited grace period. Each bit is "." - if the corresponding condition does not hold. - -o "ttb" is a single bit. It is "B" if any of the blocked tasks - need to be priority boosted and "." otherwise. - -o "btg" indicates whether boosting has been carried out during - the current grace period, with "exp" indicating that boosting - is in progress for an expedited grace period, "no" indicating - that boosting has not yet started for a normal grace period, - "begun" indicating that boosting has bebug for a normal grace - period, and "done" indicating that boosting has completed for - a normal grace period. - -o "ntb" is the total number of tasks subjected to RCU priority boosting - periods since boot. - -o "neb" is the number of expedited grace periods that have had - to resort to RCU priority boosting since boot. - -o "nnb" is the number of normal grace periods that have had - to resort to RCU priority boosting since boot. - -o "j" is the low-order 16 bits of the jiffies counter in hexadecimal. - -o "bt" is the low-order 16 bits of the value that the jiffies counter - will have at the next time that boosting is scheduled to begin. - -o In the line beginning with "normal balk", the fields are as follows: - - o "nt" is the number of times that the system balked from - boosting because there were no blocked tasks to boost. - Note that the system will balk from boosting even if the - grace period is overdue when the currently running task - is looping within an RCU read-side critical section. - There is no point in boosting in this case, because - boosting a running task won't make it run any faster. - - o "gt" is the number of times that the system balked - from boosting because, although there were blocked tasks, - none of them were preventing the current grace period - from completing. - - o "bt" is the number of times that the system balked - from boosting because boosting was already in progress. - - o "b" is the number of times that the system balked from - boosting because boosting had already completed for - the grace period in question. - - o "ny" is the number of times that the system balked from - boosting because it was not yet time to start boosting - the grace period in question. - - o "nos" is the number of times that the system balked from - boosting for inexplicable ("not otherwise specified") - reasons. This can actually happen due to races involving - increments of the jiffies counter. - -o In the line beginning with "exp balk", the fields are as follows: - - o "bt" is the number of times that the system balked from - boosting because there were no blocked tasks to boost. - - o "nos" is the number of times that the system balked from - boosting for inexplicable ("not otherwise specified") - reasons. -- cgit v1.1