linux/arch/arc/kernel
Vineet Gupta e81b75f7b2 ARC: remove SYNC from __switch_to()
SYNC in __switch_to() is a historic relic and not needed at all.

 - In UP context it is obviously useless, why would we want to stall
   the core for all updates to stack memory of t0 to complete before
   loading kernel mode callee registers from t1 stack's memory.

 - In SMP, there could be potential race in which outgoing task could
   be concurrently picked for running on a different core, thus writes
   to stack here need to be visible before the reads from stack on
   other core. Peter confirmed that generic schedular already has needed
   barriers (by way of rq lock) so there is no need for additional arch
   barrier.

This came up when Noam was trying to replace this SYNC with EZChip
specific hardware thread scheduling instruction for their platform
support.

Link: http://lkml.kernel.org/r/20151102092654.GM17308@twins.programming.kicks-ass.net
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Cc: Noam Camus <noamc@ezchip.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
2015-11-17 22:05:30 +05:30
..
.gitignore ARC: Add some .gitignore entries 2013-08-26 09:40:24 +05:30
arc_hostlink.c ARC: Hostlink Pseudo-Driver for Metaware Debugger 2013-02-15 23:16:10 +05:30
arcksyms.c
asm-offsets.c ARCv2: [vdk] dts files and defconfig for HS38 VDK 2015-06-25 06:00:21 +05:30
clk.c ARC: fix typo with clock speed 2013-05-07 13:43:54 +05:30
ctx_sw_asm.S ARC: remove SYNC from __switch_to() 2015-11-17 22:05:30 +05:30
ctx_sw.c ARC: remove SYNC from __switch_to() 2015-11-17 22:05:30 +05:30
devtree.c ARCv2: [axs103] Support ARC SDP FPGA platform for HS38x cores 2015-06-25 06:00:20 +05:30
disasm.c ARC: rename kconfig option for unaligned emulation 2014-10-13 14:46:15 +05:30
entry-arcv2.S ARC: [arcompact] Handle bus error from userspace as Interrupt not exception 2015-11-14 13:12:20 +05:30
entry-compact.S ARC: [arcompact] Handle bus error from userspace as Interrupt not exception 2015-11-14 13:12:20 +05:30
entry.S ARC: [arcompact] Handle bus error from userspace as Interrupt not exception 2015-11-14 13:12:20 +05:30
fpu.c ARC: Process-creation/scheduling/idle-loop 2013-02-11 20:00:38 +05:30
head.S ARC: boot: Non Master cpus only need to call EARLY_CPU_SETUP once 2015-10-28 16:13:42 +05:30
intc-arcv2.c arc:irqchip: prepare for drivers/irqchip/irqchip.h removal 2015-07-09 17:36:32 +05:30
intc-compact.c ARC: smp: irqchip: handle IPI as percpu irq like timer 2015-10-28 16:13:39 +05:30
irq.c ARC: smp: Introduce smp hook @init_irq_cpu called for all cores 2015-10-28 16:13:41 +05:30
kgdb.c ARC: kgdb: generic kgdb_arch_pc() suffices 2014-10-22 16:14:04 -06:00
kprobes.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-11-15 16:47:22 -08:00
Makefile ARCv2: SMP: Support ARConnect (MCIP) for Inter-Core-Interrupts et al 2015-06-22 14:06:56 +05:30
mcip.c ARCv2: smp: [plat-*]: No need to explicitly call mcip_init_smp() 2015-10-28 16:13:41 +05:30
module.c ARC: Fix coding style issues 2013-04-09 12:21:14 +05:30
perf_event.c ARCv2: perf: Finally introduce HS perf unit 2015-08-27 14:59:07 +05:30
process.c ARC: Abstract out ISA specific SLEEP args 2015-11-16 14:17:02 +05:30
ptrace.c ARCv2: Support for ARCv2 ISA and HS38x cores 2015-06-22 14:06:55 +05:30
reset.c arc: export symbol for pm_power_off in reset.c 2013-11-06 10:41:44 +05:30
setup.c ARC: smp: Introduce smp hook @init_early_smp for Master core 2015-10-28 16:13:40 +05:30
signal.c ARCv2: Support for ARCv2 ISA and HS38x cores 2015-06-22 14:06:55 +05:30
smp.c ARC: smp: Introduce smp hook @init_irq_cpu called for all cores 2015-10-28 16:13:41 +05:30
stacktrace.c ARC: stack unwinder to bail if PC is not kernel mode 2015-06-19 18:09:29 +05:30
sys.c ARC: ABIv3: fork/vfork wrappers not needed in "no-legacy-syscall" ABI 2013-03-11 19:01:10 +05:30
time.c ARC: remove @init_time, @init_irq platform callbacks 2015-10-28 16:13:39 +05:30
traps.c ARC: rename unhandled exception handler 2015-04-13 15:14:57 +05:30
troubleshoot.c ARC: fix unused var wanring 2015-07-06 11:09:01 +05:30
unaligned.c ARC: change some branchs to jumps to resolve linkage errors 2015-08-20 18:53:15 +05:30
unwind.c treewide: Fix typo in printk messages 2015-03-06 23:05:39 +01:00
vmlinux.lds.S ARC: boot: Support Halt-on-reset and Run-on-reset SMP booting modes 2015-10-28 16:08:17 +05:30