From: Tejun Heo Date: Tue, 6 Jan 2015 15:26:10 +0000 (-0500) Subject: percpu_ref: remove unnecessary ACCESS_ONCE() in percpu_ref_tryget_live() X-Git-Tag: omap-for-v4.1/prcm-dts-mfd-syscon-fix~152^2~1 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6810e4a394f9d781050107529b8d1465c00b7b13;p=pandora-kernel.git percpu_ref: remove unnecessary ACCESS_ONCE() in percpu_ref_tryget_live() __ref_is_percpu() needs the implied ACCESS_ONCE() in lockless_dereference() on @ref->percpu_count_ptr because the value is tested for !__PERCPU_REF_ATOMIC, which may be set asynchronously, and then used as a pointer. If the compiler generates a separate fetch when using it as a pointer, __PERCPU_REF_ATOMIC may be set in between contaminating the pointer value. percpu_ref_tryget_live() also uses ACCESS_ONCE() to test __PERCPU_REF_DEAD; however, there's no reason for this. I just copied ACCESS_ONCE() usage blindly from __ref_is_percpu(). All it does is confusing people trying to understand what's going on. This patch removes the unnecessary ACCESS_ONCE() usage from percpu_ref_tryget_live() and adds a comment explaining why __ref_is_percpu() needs it. Signed-off-by: Tejun Heo Cc: Kent Overstreet --- Reading git-diff-tree failed