On Mon, Jul 09, 2018 at 03:47:41PM +0300, Alexey Brodkin wrote: > Atomic instructions require data they operate on to be aligned > according to data size. I.e. 32-bit atomic values must be 32-bit > aligned while 64-bit values must be 64-bit aligned. > > Otherwise even if CPU may handle not-aligend normal data access, > still atomic instructions fail and typically raise an exception > leaving us dead in the water. > > This came-up during lengthly discussion here: > http://lists.infradead.org/pipermail/linux-snps-arc/2018-July/004022.html > > Signed-off-by: Alexey Brodkin <abrodkin at synopsys.com> > Cc: Will Deacon <will.deacon at arm.com> > Cc: Peter Zijlstra <peterz at infradead.org> > Cc: Boqun Feng <boqun.feng at gmail.com> > Cc: Russell King <linux at armlinux.org.uk> > Cc: Arnd Bergmann <arnd at arndb.de> > Cc: Thomas Gleixner <tglx at linutronix.de> > Cc: Ingo Molnar <mingo at redhat.com> > Cc: Darren Hart <dvhart at infradead.org> > Cc: Shuah Khan <shuah at kernel.org> > Cc: "Paul E. McKenney" <paulmck at linux.vnet.ibm.com> > Cc: Josh Triplett <josh at joshtriplett.org> > Cc: Steven Rostedt <rostedt at goodmis.org> > Cc: Mathieu Desnoyers <mathieu.desnoyers at efficios.com> > Cc: Lai Jiangshan <jiangshanlai at gmail.com> > Cc: David Laight <David.Laight at ACULAB.COM> > Cc: Geert Uytterhoeven <geert at linux-m68k.org> > Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org> > --- > arch/arm/include/asm/atomic.h | 2 +- > include/asm-generic/atomic64.h | 2 +- > include/linux/types.h | 4 ++-- > tools/include/linux/types.h | 2 +- > tools/testing/selftests/futex/include/atomic.h | 2 +- > .../rcutorture/formal/srcu-cbmc/include/linux/types.h | 4 ++-- > 6 files changed, 8 insertions(+), 8 deletions(-) > > diff --git a/arch/arm/include/asm/atomic.h b/arch/arm/include/asm/atomic.h > index 66d0e215a773..2ed6d7cf1407 100644 > --- a/arch/arm/include/asm/atomic.h > +++ b/arch/arm/include/asm/atomic.h > @@ -267,7 +267,7 @@ ATOMIC_OPS(xor, ^=, eor) > > #ifndef CONFIG_GENERIC_ATOMIC64 > typedef struct { > - long long counter; > + u64 __aligned(8) counter; > } atomic64_t; Long long is 8-byte aligned per EABI ARM, and we use the generic atomic64 infrastructure for OABI, so we don't need to change anything here afaict. Will
