From: Li Zhe <lizhe.67@xxxxxxxxxxxxx> In the current kernel rwsem implementation, there is an interface to downgrade write lock to read lock, but there is no interface to upgrade a read lock to write lock. This means that in order to acquire write lock while holding read lock, we have to release the read lock first and then acquire the write lock, which will introduce some troubles in concurrent programming. This patch set provides the 'upgrade_read' interface to solve this problem. This interface can change a read lock to a write lock. Li Zhe (2): rwsem: introduce upgrade_read interface khugepaged: use upgrade_read() to optimize collapse_huge_page include/linux/rwsem.h | 1 + kernel/locking/rwsem.c | 87 ++++++++++++++++++++++++++++++++++++++++-- mm/khugepaged.c | 36 ++++++++--------- 3 files changed, 104 insertions(+), 20 deletions(-) -- 2.20.1
