Messages in this thread | | | From | Andi Kleen <> | Subject | [PATCH] [0/11] SYSCTL: Use RCU to avoid races with string sysctls | Date | Mon, 21 Dec 2009 02:20:21 +0100 (CET) |
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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.
-Andi
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