On Tue, Sep 22, 2020 at 07:43:30PM -0600, Shuah Khan wrote: > Introduce Simple atomic and non-atomic counters. > > There are a number of atomic_t usages in the kernel where atomic_t api > is used strictly for counting and not for managing object lifetime. In > some cases, atomic_t might not even be needed. > > The purpose of these counters is twofold: 1. clearly differentiate > atomic_t counters from atomic_t usages that guard object lifetimes, > hence prone to overflow and underflow errors. It allows tools that scan > for underflow and overflow on atomic_t usages to detect overflow and > underflows to scan just the cases that are prone to errors. 2. provides > non-atomic counters for cases where atomic isn't necessary. > > Simple atomic and non-atomic counters api provides interfaces for simple > atomic and non-atomic counters that just count, and don't guard resource > lifetimes. Counters will wrap around to 0 when it overflows and should > not be used to guard resource lifetimes, device usage and open counts > that control state changes, and pm states. > > Using counter_atomic to guard lifetimes could lead to use-after free > when it overflows and undefined behavior when used to manage state > changes and device usage/open states. > > Signed-off-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx> > --- > Documentation/core-api/counters.rst | 158 +++++++++++++ > MAINTAINERS | 7 + > include/linux/counters.h | 343 ++++++++++++++++++++++++++++ > lib/Kconfig | 10 + > lib/Makefile | 1 + > lib/test_counters.c | 283 +++++++++++++++++++++++ Tests for new apis, nice! Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
