diff options
author | Mark Rutland <mark.rutland@arm.com> | 2017-09-26 12:41:52 +0100 |
---|---|---|
committer | Tejun Heo <tj@kernel.org> | 2017-09-26 07:37:33 -0700 |
commit | e88d62cd4b2f0b1ae55e9008e79c2794b1fc914d (patch) | |
tree | 30bdd02e4d4fd3a7c4a1f03aca0f77c48d8b094f /mm | |
parent | e365806ac289457263a133bd32df8df49897f612 (diff) | |
download | linux-e88d62cd4b2f0b1ae55e9008e79c2794b1fc914d.tar.bz2 |
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