Ping? :) (2014/08/25 19:55), Masami Hiramatsu wrote: > Hi, > > Here is a series of patches which remove stop_machine() from > module unloading. > > Currently, each module unloading calls stop_machine()s 2 times. > One is for safely removing module from lists and one is to > check the reference counter. However, both are not necessary > for those purposes (required by current implementation). > > First, we can use RCU for the list operation, we just need > a synchronize_rcu right before cleaning up. > Second, the reference counter can be checked atomically by > using atomic_t, instead of per-cpu module_ref. Of course, > for BIG SMP machines, atomic operation is not efficient. > However, they usually don't need to remove most of modules too. > > In this series, I just fixed to use RCU for the module(and > bugs) list for the first stop_machine. > And for the second one, I replaced module_ref with atomic_t > and introduced a "module lockup" module load option, which > makes a module un-removable (lock up the module in kernel). > The lockup modules can not be removed except forced, and the > kernel skips module refcounting on those modules. Thus we > can minimize the performance impact on the BIG SMP machines. > > BTW, of course this requires to update libkmod to support > new MODULE_INIT_LOCKUP_MODULE flag. I'm not sure where is > good to send the patches I have. Sould I better sending > kmod patches on LKML? > > Thank you, > > --- > > Masami Hiramatsu (5): > module: Wait for RCU synchronizing before releasing a module > module: Unlink module with RCU synchronizing instead of stop_machine > lib/bug: Use RCU list ops for module_bug_list > module: Lock up a module when loading with a LOCLUP flag > module: Remove stop_machine from module unloading > > > include/linux/module.h | 22 ++---- > include/trace/events/module.h | 2 - > include/uapi/linux/module.h | 1 > kernel/module.c | 147 > +++++++++++++++++------------------------ > lib/bug.c | 20 ++++-- > 5 files changed, 85 insertions(+), 107 deletions(-) > > -- > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
-- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu...@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
