From 4c677e2eefdba9c5bfc4474e2e91b26ae8458a1d Mon Sep 17 00:00:00 2001 From: Vasiliy Kulikov Date: Fri, 29 Jul 2011 03:56:40 +0400 Subject: [PATCH] shm: optimize locking and ipc_namespace getting shm_lock() does a lookup of shm segment in shm_ids(ns).ipcs_idr, which is redundant as we already know shmid_kernel address. An actual lock is also not required for reads until we really want to destroy the segment. exit_shm() and shm_destroy_orphaned() may avoid the loop by checking whether there is at least one segment in current ipc_namespace. The check of nsproxy and ipc_ns against NULL is redundant as exit_shm() is called from do_exit() before the call to exit_notify(), so the dereferencing current->nsproxy->ipc_ns is guaranteed to be safe. Reported-by: Oleg Nesterov Signed-off-by: Vasiliy Kulikov Acked-by: Serge Hallyn Signed-off-by: Linus Torvalds --- Reading git-format-patch failed