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authorPaul E. McKenney <paulmck@linux.ibm.com>2018-11-29 13:28:49 -0800
committerPaul E. McKenney <paulmck@linux.ibm.com>2019-01-25 15:28:30 -0800
commit260e1e4fd826a8e47c8976efba6a54d62b4a57de (patch)
treec9e6ac47f789562966eed2eea94da1593440bc7f /Documentation/RCU
parent892307266429f6439803f2735a59a4bc58a6ded4 (diff)
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rcu: Discard separate per-CPU callback counts
Back when there were multiple flavors of RCU, it was necessary to separately count lazy and non-lazy callbacks for each CPU. These counts were used in CONFIG_RCU_FAST_NO_HZ kernels to determine how long a newly idle CPU should be allowed to sleep before handling its RCU callbacks. But now that there is only one flavor, the callback counts for a given CPU's sole rcu_data structure are the counts for that CPU. This commit therefore removes the rcu_data structure's ->nonlazy_posted and ->nonlazy_posted_snap fields, the rcu_idle_count_callbacks_posted() and rcu_cpu_has_callbacks() functions, repurposes the rcu_data structure's ->all_lazy field to record the laziness state at the beginning of the latest idle sojourn, and modifies CONFIG_RCU_FAST_NO_HZ RCU CPU stall warnings accordingly. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Diffstat (limited to 'Documentation/RCU')
-rw-r--r--Documentation/RCU/stallwarn.txt15
1 files changed, 8 insertions, 7 deletions
diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt
index 073dbc12d1ea..1ab70c37921f 100644
--- a/Documentation/RCU/stallwarn.txt
+++ b/Documentation/RCU/stallwarn.txt
@@ -219,17 +219,18 @@ an estimate of the total number of RCU callbacks queued across all CPUs
In kernels with CONFIG_RCU_FAST_NO_HZ, more information is printed
for each CPU:
- 0: (64628 ticks this GP) idle=dd5/3fffffffffffffff/0 softirq=82/543 last_accelerate: a345/d342 nonlazy_posted: 25 .D
+ 0: (64628 ticks this GP) idle=dd5/3fffffffffffffff/0 softirq=82/543 last_accelerate: a345/d342 Nonlazy posted: ..D
The "last_accelerate:" prints the low-order 16 bits (in hex) of the
jiffies counter when this CPU last invoked rcu_try_advance_all_cbs()
from rcu_needs_cpu() or last invoked rcu_accelerate_cbs() from
-rcu_prepare_for_idle(). The "nonlazy_posted:" prints the number
-of non-lazy callbacks posted since the last call to rcu_needs_cpu().
-Finally, an "L" indicates that there are currently no non-lazy callbacks
-("." is printed otherwise, as shown above) and "D" indicates that
-dyntick-idle processing is enabled ("." is printed otherwise, for example,
-if disabled via the "nohz=" kernel boot parameter).
+rcu_prepare_for_idle(). The "Nonlazy posted:" indicates lazy-callback
+status, so that an "l" indicates that all callbacks were lazy at the start
+of the last idle period and an "L" indicates that there are currently
+no non-lazy callbacks (in both cases, "." is printed otherwise, as
+shown above) and "D" indicates that dyntick-idle processing is enabled
+("." is printed otherwise, for example, if disabled via the "nohz="
+kernel boot parameter).
If the grace period ends just as the stall warning starts printing,
there will be a spurious stall-warning message, which will include