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authorMark Rutland <mark.rutland@arm.com>2017-09-26 14:41:52 +0300
committerTejun Heo <tj@kernel.org>2017-09-26 17:37:33 +0300
commite88d62cd4b2f0b1ae55e9008e79c2794b1fc914d (patch)
tree30bdd02e4d4fd3a7c4a1f03aca0f77c48d8b094f /mm
parente365806ac289457263a133bd32df8df49897f612 (diff)
downloadlinux-e88d62cd4b2f0b1ae55e9008e79c2794b1fc914d.tar.xz
percpu: make this_cpu_generic_read() atomic w.r.t. interrupts
As raw_cpu_generic_read() is a plain read from a raw_cpu_ptr() address, it's possible (albeit unlikely) that the compiler will split the access across multiple instructions. In this_cpu_generic_read() we disable preemption but not interrupts before calling raw_cpu_generic_read(). Thus, an interrupt could be taken in the middle of the split load instructions. If a this_cpu_write() or RMW this_cpu_*() op is made to the same variable in the interrupt handling path, this_cpu_read() will return a torn value. For native word types, we can avoid tearing using READ_ONCE(), but this won't work in all cases (e.g. 64-bit types on most 32-bit platforms). This patch reworks this_cpu_generic_read() to use READ_ONCE() where possible, otherwise falling back to disabling interrupts. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Christoph Lameter <cl@linux.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Pranith Kumar <bobby.prani@gmail.com> Cc: Tejun Heo <tj@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-arch@vger.kernel.org Cc: stable@vger.kernel.org Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'mm')
0 files changed, 0 insertions, 0 deletions