|| ||Andi Kleen <email@example.com> |
|| ||firstname.lastname@example.org, email@example.com,
|| ||[PATCH] [0/11] SYSCTL: Use RCU to avoid races with string sysctls |
|| ||Mon, 21 Dec 2009 02:20:21 +0100 (CET)|
|| ||Article, Thread
With BKL-less sysctls most of the writable string sysctls are racy. There
is no locking on the reader side, so a reader could see an inconsistent
string or worse miss the terminating null and walk of beyond it.
This patch kit adds a new "rcu string" variant to avoid these
problems and convers the racy users. One the writer side the strings are
always copied to new memory and the readers use rcu_read_lock()
to get a stable view. For readers who access the string over
sleeps the reader copies the string.
This is all hidden in a new generic "rcu_string" ADT which can be also
used for other purposes.
This finally implements all the letters in RCU, most other users
leave out the 'C'.
I also fixed the zone order list sysctl to use a mutex to avoid
racing with itself.
I left some obscure users in architectures (sparc, mips) alone and audited
all of the others. The sparc reboot_cmd one has references to asm files
which I didn't want to touch and the mips variant seemd just too obscure.
All the others are not racy.
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