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author | Linus Torvalds <torvalds@linux-foundation.org> | 2010-10-21 12:54:12 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-10-21 12:54:12 -0700 |
commit | 888a6f77e0418b049f83d37547c209b904d30af4 (patch) | |
tree | 42cdb9f781d2177e6b380e69a66a27ec7705f51f /Documentation/RCU/stallwarn.txt | |
parent | 31b7eab27a314b153d8fa07ba9e9ec00a98141e1 (diff) | |
parent | 6506cf6ce68d78a5470a8360c965dafe8e4b78e3 (diff) | |
download | op-kernel-dev-888a6f77e0418b049f83d37547c209b904d30af4.zip op-kernel-dev-888a6f77e0418b049f83d37547c209b904d30af4.tar.gz |
Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (52 commits)
sched: fix RCU lockdep splat from task_group()
rcu: using ACCESS_ONCE() to observe the jiffies_stall/rnp->qsmask value
sched: suppress RCU lockdep splat in task_fork_fair
net: suppress RCU lockdep false positive in sock_update_classid
rcu: move check from rcu_dereference_bh to rcu_read_lock_bh_held
rcu: Add advice to PROVE_RCU_REPEATEDLY kernel config parameter
rcu: Add tracing data to support queueing models
rcu: fix sparse errors in rcutorture.c
rcu: only one evaluation of arg in rcu_dereference_check() unless sparse
kernel: Remove undead ifdef CONFIG_DEBUG_LOCK_ALLOC
rcu: fix _oddness handling of verbose stall warnings
rcu: performance fixes to TINY_PREEMPT_RCU callback checking
rcu: upgrade stallwarn.txt documentation for CPU-bound RT processes
vhost: add __rcu annotations
rcu: add comment stating that list_empty() applies to RCU-protected lists
rcu: apply TINY_PREEMPT_RCU read-side speedup to TREE_PREEMPT_RCU
rcu: combine duplicate code, courtesy of CONFIG_PREEMPT_RCU
rcu: Upgrade srcu_read_lock() docbook about SRCU grace periods
rcu: document ways of stalling updates in low-memory situations
rcu: repair code-duplication FIXMEs
...
Diffstat (limited to 'Documentation/RCU/stallwarn.txt')
-rw-r--r-- | Documentation/RCU/stallwarn.txt | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt index 44c6dcc9..862c08e 100644 --- a/Documentation/RCU/stallwarn.txt +++ b/Documentation/RCU/stallwarn.txt @@ -80,6 +80,24 @@ o A CPU looping with bottom halves disabled. This condition can o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the kernel without invoking schedule(). +o A CPU-bound real-time task in a CONFIG_PREEMPT kernel, which might + happen to preempt a low-priority task in the middle of an RCU + read-side critical section. This is especially damaging if + that low-priority task is not permitted to run on any other CPU, + in which case the next RCU grace period can never complete, which + will eventually cause the system to run out of memory and hang. + While the system is in the process of running itself out of + memory, you might see stall-warning messages. + +o A CPU-bound real-time task in a CONFIG_PREEMPT_RT kernel that + is running at a higher priority than the RCU softirq threads. + This will prevent RCU callbacks from ever being invoked, + and in a CONFIG_TREE_PREEMPT_RCU kernel will further prevent + RCU grace periods from ever completing. Either way, the + system will eventually run out of memory and hang. In the + CONFIG_TREE_PREEMPT_RCU case, you might see stall-warning + messages. + o A bug in the RCU implementation. o A hardware failure. This is quite unlikely, but has occurred |