Read-Copy-Update is a sync mechanism allowing reads to occur concurrently with updates. It maintains multiple versions of objects and ensures they aren't freed until all preexisting read-side crit-sections complete. Since write to aligned pointer is atomic, we can atomic insert, remove, replace data items in a linked struct without disrupting readers. Concurrent readers can then continue accessing the old version, new readers will see updated version.
Questions tagged [rcu]
52 questions
1
vote
0 answers
MDS and BIPLATFORM repositories are not found while installing through RCU
I am aiming to install OBIEE 11g.
1) I installed Oracle DB 11
2) Installed Oracle SQL Developer
3) Tested the connectivity and it worked
4) I have SYS, SYSDBA users running well with all the privileges
5) I downloaded RCU from Oracle for Windows 64…
suj
- 507
- 1
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0
votes
1 answer
Does using list_for_each_entry() in rcu reader side critical section cause problems?
In the Linux kernel, list_for_each_entry_rcu() is used to traverse rcu protected list in reader side critical section. What happens if list_for_each_entry() is used instead? Does it cause problems?
hdthky
- 57
- 1
- 4
0
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0 answers
How to disable CONFIG_PREEMPT_RCU in 5.14 kernel
Facing below warning message in 5.14 kernel module while taking rcu_read_lock()/unlock(), but the same code is working in 3.14 kernel.
[ +0.000004] Voluntary context switch within RCU read-side critical section!
[ +0.000005] WARNING: CPU: 3 PID:…
user1720713
- 184
- 8
0
votes
1 answer
Return a pointer from RCU-protected list in LKM
I'm a bit confused about such code:
struct a {
// ...
struct list_head some_list;
// ...
};
struct e {
struct list_head next;
// ...
};
static void *traverse(struct a *a)
{
struct e *e;
rcu_read_lock();
…
k1r1t0
- 465
- 2
- 11
0
votes
0 answers
The Linux(CentOS 7.9) kernel has prompted a bug. Is it harmful?
My runtime environment is CentOS 7.9(kernel is version 5.16.11) in the VMBox virtual machine, it is allocated 1G memory and 8 CPU cores.
[root@dev236 ~]# uname -a
Linux dev236 5.16.11-1.el7.elrepo.x86_64 #1 SMP PREEMPT Tue Feb 22 10:22:37 EST 2022…
czg
- 45
- 3
0
votes
0 answers
rcu_sched vs rcu_preempt CPU stalls
I have basic query regarding the RCU CPU stalls, sometimes there is message like INFO: rcu_sched self-detected stall on CPU, and sometimes it's INFO: rcu_preempt detected stall on CPUs/task, what is the difference between these two?
Is it dependent…
Milan
- 1,447
- 5
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- 27
0
votes
0 answers
where and how grace period for Linux RCU's is initialized and accounted?
Trying to understand, how and where grace period in an RCU is initialized. Is there a static declaration somewhere in Linux Kernel to define the grace period, or are there some other complex ways to do this, for example as per this small snippet:
…
Milan
- 1,447
- 5
- 19
- 27
0
votes
1 answer
Is it possible to create new RCU schemas for an existing Domain?
So basically I have a OSB domain, and the DB is going to be decommissioned and a new one will be created.
Is it possible to generate a new RCU on the new DB and then only replace the DB info on the the existing domain? Or should we migrate the…
OverlOrDGT PT
- 13
- 5
0
votes
0 answers
Why RCU is designed to protect pointer assignment?
I am wondering Why RCU is designed to protect pointer assignment and access. If the rcu_read_lock is used to protect to normal varliable access, what will happen?
river
- 694
- 6
- 22
0
votes
2 answers
'c:\Program' is not recognized as an internal or external command, operable command or batch file
After successful installation of Oracle SOA Suite 12c, I'm trying to install RCU.
When I try to execute an RCU batch file from the command prompt, I get this error:
'c:\Program' is not recognized as an internal or external command, operable command…
Meena
- 93
- 4
- 10
0
votes
0 answers
Can we link a new RCU with an old weblogic Domain
Can we link a new RCU with an old weblogic Domain. Imagine a scenario where I remove a RCU from DB but the domain is already there. After creating a new RCU how do I sync/reconfigure it with old Domain?
Devansh Jani
- 57
- 1
- 10
0
votes
1 answer
How RCU handles the condition of a reader started reading critical section while synchronize_rcu() is waiting
As per the RCU documentation (I believe kernel and userspace RCU frameworks are similar), synchronize_rcu() waits for all the readers (who started before synchronize_rcu was called ) to finish.
What happens to the readers which are started after…
Franc
- 319
- 9
- 28
0
votes
0 answers
why does `synchronize_rcu()` not deadlock when beening called inside a read lock block?
synchronize_rcu() is used to waits only for ongoing RCU read-side critical sections to complete. If so, it should been blocked forever when beening called inside a read block. However, the following code works well on my linux kernel, why?
void…
river
- 694
- 6
- 22
0
votes
0 answers
Adding and finding rcu node from a rcu list
I am trying to add rcu node into rcu_list by calling a function , hlist_add_head_rcu, with rcu_list's own lock and spin_lock.
After that, i need to check whether the rcu node is on pending for assigning into rcu_list before calling a reclaimer…
Youngwook
- 11
- 4
0
votes
1 answer
gcc show "Need native word sized stores/loads for atomicity" for calling `hlist_nulls_add_head_rcu`
I want to call hlist_nulls_add_head_rcu to manage my list, however gcc gives lots of error messages as following:
|| ./include/linux/rculist_nulls.h: In function…
river
- 694
- 6
- 22