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Paul Mackerras 9fb1b36ca1 powerpc: Make sure IPI handlers see data written by IPI senders 
We have been observing hangs, both of KVM guest vcpu tasks and more
generally, where a process that is woken doesn't properly wake up and
continue to run, but instead sticks in TASK_WAKING state.  This
happens because the update of rq->wake_list in ttwu_queue_remote()
is not ordered with the update of ipi_message in
smp_muxed_ipi_message_pass(), and the reading of rq->wake_list in
scheduler_ipi() is not ordered with the reading of ipi_message in
smp_ipi_demux().  Thus it is possible for the IPI receiver not to see
the updated rq->wake_list and therefore conclude that there is nothing
for it to do.

In order to make sure that anything done before smp_send_reschedule()
is ordered before anything done in the resulting call to scheduler_ipi(),
this adds barriers in smp_muxed_message_pass() and smp_ipi_demux().
The barrier in smp_muxed_message_pass() is a full barrier to ensure that
there is a full ordering between the smp_send_reschedule() caller and
scheduler_ipi().  In smp_ipi_demux(), we use xchg() rather than
xchg_local() because xchg() includes release and acquire barriers.
Using xchg() rather than xchg_local() makes sense given that
ipi_message is not just accessed locally.

This moves the barrier between setting the message and calling the
cause_ipi() function into the individual cause_ipi implementations.
Most of them -- those that used outb, out_8 or similar -- already had
a full barrier because out_8 etc. include a sync before the MMIO
store.  This adds an explicit barrier in the two remaining cases.

These changes made no measurable difference to the speed of IPIs as
measured using a simple ping-pong latency test across two CPUs on
different cores of a POWER7 machine.

The analysis of the reason why processes were not waking up properly
is due to Milton Miller.

Cc: stable@vger.kernel.org # v3.0+
Reported-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
 		2012-09-05 16:05:22 +10:00
..
vdso32 powerpc: Add VDSO version of getcpu 2012-07-11 14:18:40 +10:00
vdso64 powerpc: Add VDSO version of getcpu 2012-07-11 14:18:40 +10:00
.gitignore
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Makefile KVM: PPC: Factor out guest epapr initialization 2012-05-30 11:43:10 +02:00
align.c Disintegrate asm/system.h for PowerPC 2012-03-28 18:30:02 +01:00
asm-offsets.c powerpc: Restore correct DSCR in context switch 2012-09-05 16:05:22 +10:00
audit.c
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btext.c powerpc: various straight conversions from module.h --> export.h 2011-10-31 19:30:44 -04:00
cacheinfo.c cpu: convert 'cpu' and 'machinecheck' sysdev_class to a regular subsystem 2011-12-21 14:29:42 -08:00
cacheinfo.h
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clock.c powerpc: various straight conversions from module.h --> export.h 2011-10-31 19:30:44 -04:00
compat_audit.c
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cpu_setup_6xx.S powerpc: Fix some 6xx/7xxx CPU setup functions 2011-02-07 12:57:11 +11:00
cpu_setup_44x.S powerpc/44x: Add support for the AMCC APM821xx SoC 2010-10-13 08:47:09 -04:00
cpu_setup_a2.S powerpc: Enforce usage of RA 0-R31 where possible 2012-07-10 19:18:35 +10:00
cpu_setup_fsl_booke.S KVM: PPC: e500mc support 2012-04-08 12:54:33 +03:00
cpu_setup_pa6t.S
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cpu_setup_power7.S powerpc, KVM: Split HVMODE_206 cpu feature bit into separate HV and architecture bits 2011-07-12 13:16:58 +03:00
cpu_setup_ppc970.S powerpc, KVM: Split HVMODE_206 cpu feature bit into separate HV and architecture bits 2011-07-12 13:16:58 +03:00
cputable.c Disintegrate asm/system.h for PowerPC 2012-03-28 18:30:02 +01:00
crash.c Disintegrate asm/system.h for PowerPC 2012-03-28 18:30:02 +01:00
crash_dump.c powerpc: Rename mapping based RELOCATABLE to DYNAMIC_MEMSTART for BookE 2011-12-20 10:20:19 -05:00
dbell.c powerpc: Make sure IPI handlers see data written by IPI senders 2012-09-05 16:05:22 +10:00
dma-iommu.c powerpc/dma-iommu: Fix IOMMU window check 2012-08-24 20:26:07 +10:00
dma-swiotlb.c common: dma-mapping: add support for generic dma_mmap_* calls 2012-07-30 12:25:46 +02:00
dma.c Merge branch 'for-linus-for-3.6-rc1' of git://git.linaro.org/people/mszyprowski/linux-dma-mapping 2012-07-30 10:11:31 -07:00
entry_32.S powerpc: Set stack limit properly in crit_transfer_to_handler 2012-07-27 11:42:31 +10:00
entry_64.S powerpc: Restore correct DSCR in context switch 2012-09-05 16:05:22 +10:00
epapr_hcalls.S KVM: PPC: Factor out guest epapr initialization 2012-05-30 11:43:10 +02:00
epapr_paravirt.c KVM: PPC: Factor out guest epapr initialization 2012-05-30 11:43:10 +02:00
exceptions-64e.S powerpc: Use CURRENT_THREAD_INFO instead of open coded assembly 2012-07-11 14:18:22 +10:00
exceptions-64s.S powerpc: Give hypervisor decrementer interrupts their own handler 2012-09-05 16:05:19 +10:00
fadump.c powerpc: Fix fallout from system.h split up 2012-04-02 14:00:03 +10:00
firmware.c powerpc: fix implicit use of cache.h in kernel/firmware.c 2011-10-31 19:30:41 -04:00
fpu.S powerpc: Enforce usage of R0-R31 where possible 2012-07-10 19:18:30 +10:00
fsl_booke_entry_mapping.S powerpc/fsl-booke: Fix address issue when using relocatable kernels 2010-07-11 11:04:08 -05:00
ftrace.c powerpc/ftrace: Trace function graph entry before updating index 2012-07-27 11:42:34 +10:00
head_8xx.S powerpc: Call do_page_fault() with interrupts off 2012-03-09 10:55:08 +11:00
head_32.S powerpc: Call do_page_fault() with interrupts off 2012-03-09 10:55:08 +11:00
head_40x.S powerpc: Call do_page_fault() with interrupts off 2012-03-09 10:55:08 +11:00
head_44x.S Merge branch 'next' of git://git.kernel.org/pub/scm/virt/kvm/kvm 2012-05-24 16:17:30 -07:00
head_64.S powerpc: Rework lazy-interrupt handling 2012-03-09 13:25:06 +11:00
head_booke.h KVM: PPC: booke: category E.HV (GS-mode) support 2012-04-08 12:51:19 +03:00
head_fsl_booke.S Merge remote-tracking branch 'kumar/next' into next 2012-07-13 13:38:26 +10:00
hw_breakpoint.c powerpc: Fix null pointer deref in perf hardware breakpoints 2012-08-24 20:26:04 +10:00
ibmebus.c Merge branch 'for-linus' of git://git.linaro.org/people/mszyprowski/linux-dma-mapping 2012-04-04 17:13:43 -07:00
idle.c powerpc: Remove unused cpu_idle_wait() 2012-05-08 12:35:07 +02:00
idle_6xx.S powerpc: Use CURRENT_THREAD_INFO instead of open coded assembly 2012-07-11 14:18:22 +10:00
idle_book3e.S powerpc: Use CURRENT_THREAD_INFO instead of open coded assembly 2012-07-11 14:18:22 +10:00
idle_e500.S powerpc: Use CURRENT_THREAD_INFO instead of open coded assembly 2012-07-11 14:18:22 +10:00
idle_power4.S powerpc: Use CURRENT_THREAD_INFO instead of open coded assembly 2012-07-11 14:18:22 +10:00
idle_power7.S powerpc/powernv: Always go into nap mode when CPU is offline 2012-09-05 16:05:20 +10:00
io-workarounds.c powerpc: io-workarounds.c was implicitly getting init_mm 2011-10-31 19:30:37 -04:00
io.c powerpc: various straight conversions from module.h --> export.h 2011-10-31 19:30:44 -04:00
iomap.c powerpc: switch to GENERIC_PCI_IOMAP 2011-11-28 21:13:18 +02:00
iommu.c powerpc/iommu: Fix iommu pool initialization 2012-07-13 17:45:49 +10:00
irq.c powerpc: Fix build of some debug irq code 2012-07-10 19:16:20 +10:00
isa-bridge.c powerpc: Remove FW_FEATURE ISERIES from arch code 2012-03-21 11:16:11 +11:00
jump_label.c powerpc: Fix build breakage in jump_label.c 2011-11-16 14:25:19 +11:00
kgdb.c powerpc/kgdb: Restore current_thread_info properly 2012-08-24 20:26:06 +10:00
kprobes.c Disintegrate asm/system.h for PowerPC 2012-03-28 18:30:02 +01:00
kvm.c KVM updates for the 3.6 merge window 2012-07-24 12:01:20 -07:00
kvm_emul.S KVM: PPC: Not optimizing MSR_CE and MSR_ME with paravirt. 2012-05-30 11:43:11 +02:00
l2cr_6xx.S Fix common misspellings 2011-03-31 11:26:23 -03:00
legacy_serial.c powerpc: Fix build on some non-freescale platforms 2012-01-25 13:33:22 +11:00
lparcfg.c Disintegrate asm/system.h for PowerPC 2012-03-28 18:30:02 +01:00
machine_kexec.c powerpc/irqdomain: Fix broken NR_IRQ references 2012-04-30 10:45:26 +10:00
machine_kexec_32.c treewide: convert uses of ATTRIB_NORETURN to __noreturn 2012-01-12 20:13:03 -08:00
machine_kexec_64.c treewide: convert uses of ATTRIB_NORETURN to __noreturn 2012-01-12 20:13:03 -08:00
misc.S powerpc: Remove legacy iSeries bits from assembly files 2012-03-09 10:54:59 +11:00
misc_32.S powerpc: Use CURRENT_THREAD_INFO instead of open coded assembly 2012-07-11 14:18:22 +10:00
misc_64.S powerpc: Fixes for instructions not using correct register naming 2012-07-10 19:18:16 +10:00
module.c powerpc: remove non-required uses of include <linux/module.h> 2011-10-31 19:30:44 -04:00
module_32.c powerpc: Fix kernel panic during kernel module load 2012-06-08 19:59:08 +10:00
module_64.c modules: make arch's use default loader hooks 2011-07-24 22:06:04 +09:30
msi.c
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nvram_64.c powerpc/nvram: Generalize code for OS partitions in NVRAM 2011-03-04 18:19:04 +11:00
of_platform.c powerpc/eeh: Introduce EEH device 2012-03-09 11:39:29 +11:00
paca.c powerpc: Remove iseries specific fields in lppaca 2012-04-30 15:37:16 +10:00
pci-common.c PCI changes for the 3.6 merge window: 2012-07-24 16:17:07 -07:00
pci_32.c powerpc/PCI: compute I/O space bus-to-resource offset consistently 2012-03-20 10:41:44 -07:00
pci_64.c PCI: replace struct pci_bus secondary/subordinate with busn_res 2012-06-13 15:42:22 -06:00
pci_dn.c powerpc/powernv: PCI support for p7IOC under OPAL v2 2011-11-25 14:53:15 +11:00
pci_of_scan.c PCI changes for the 3.6 merge window: 2012-07-24 16:17:07 -07:00
pmc.c bug.h: add include of it to various implicit C users 2012-02-29 17:15:08 -05:00
ppc32.h
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ppc_ksyms.c powerpc: Use the new generic strncpy_from_user() and strnlen_user() 2012-05-27 21:00:07 -07:00
ppc_save_regs.S Fix common misspellings 2011-03-31 11:26:23 -03:00
proc_powerpc.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
process.c powerpc: Fix DSCR inheritance in copy_thread() 2012-09-05 16:05:21 +10:00
prom.c Disintegrate asm/system.h for PowerPC 2012-03-28 18:30:02 +01:00
prom_init.c powerpc: Fix Section mismatch warnings in prom_init.c 2012-06-29 14:35:36 +10:00
prom_init_check.sh powerpc/powernv: Get kernel command line accross OPAL takeover 2011-09-20 16:09:48 +10:00
prom_parse.c powerpc: remove non-required uses of include <linux/module.h> 2011-10-31 19:30:44 -04:00
ptrace.c Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc 2012-05-23 09:02:42 -07:00
ptrace32.c powerpc: Remove old powerpc specific ptrace getregs/setregs calls 2012-04-30 15:37:28 +10:00
reloc_32.S powerpc: Process dynamic relocations for kernel 2011-12-20 10:21:08 -05:00
reloc_64.S
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rtas-proc.c powerpc: Move /proc/ppc64 to /proc/powerpc update 2010-01-15 13:26:17 +11:00
rtas-rtc.c powerpc/rtas-rtc: remove sideeffects of printk_ratelimit 2011-06-29 15:30:43 +10:00
rtas.c Disintegrate and delete asm/system.h 2012-03-28 15:58:21 -07:00
rtas_flash.c powerpc: Lack of firmware flash support is not an error 2012-07-27 11:42:33 +10:00
rtas_pci.c Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci 2012-03-23 14:02:12 -07:00
rtasd.c powerpc/pseries: Cancel RTAS event scan before firmware flash 2011-11-25 14:11:29 +11:00
setup-common.c powerpc/watchdog: move booke watchdog param related code to setup-common.c 2012-07-11 07:44:03 -05:00
setup.h
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setup_32.c powerpc/watchdog: move booke watchdog param related code to setup-common.c 2012-07-11 07:44:03 -05:00
setup_64.c Disintegrate and delete asm/system.h 2012-03-28 15:58:21 -07:00
signal.c new helper: signal_delivered() 2012-06-01 12:58:52 -04:00
signal.h powerpc: get rid of restore_sigmask() 2012-06-01 12:58:51 -04:00
signal_32.c powerpc: get rid of restore_sigmask() 2012-06-01 12:58:51 -04:00
signal_64.c powerpc: get rid of restore_sigmask() 2012-06-01 12:58:51 -04:00
smp-tbsync.c atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
smp.c powerpc: Make sure IPI handlers see data written by IPI senders 2012-09-05 16:05:22 +10:00
softemu8xx.c Disintegrate asm/system.h for PowerPC 2012-03-28 18:30:02 +01:00
stacktrace.c powerpc: various straight conversions from module.h --> export.h 2011-10-31 19:30:44 -04:00
suspend.c update email address 2010-07-19 10:56:54 +02:00
swsusp.c Disintegrate asm/system.h for PowerPC 2012-03-28 18:30:02 +01:00
swsusp_32.S Fix common misspellings 2011-03-31 11:26:23 -03:00
swsusp_64.c Disintegrate asm/system.h for PowerPC 2012-03-28 18:30:02 +01:00
swsusp_asm64.S
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swsusp_booke.S powerpc/fsl-booke: Add hibernation support for FSL BookE processors 2010-05-21 07:41:53 -05:00
sys_ppc32.c Disintegrate asm/system.h for PowerPC 2012-03-28 18:30:02 +01:00
syscalls.c powerpc: Fix personality handling in ppc64_personality() 2012-08-24 20:26:07 +10:00
sysfs.c powerpc: Keep thread.dscr and thread.dscr_inherit in sync 2012-09-05 16:05:21 +10:00
systbl.S
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systbl_chk.c
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systbl_chk.sh
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tau_6xx.c tree-wide: fix assorted typos all over the place 2009-12-04 15:39:55 +01:00
time.c powerpc: Give hypervisor decrementer interrupts their own handler 2012-09-05 16:05:19 +10:00
traps.c powerpc: Keep thread.dscr and thread.dscr_inherit in sync 2012-09-05 16:05:21 +10:00
udbg.c powerpc: Random little legacy iSeries removal tidy ups 2012-03-28 11:33:23 +11:00
udbg_16550.c powerpc: Add early debug for WSP platforms 2011-05-06 13:32:41 +10:00
vdso.c powerpc: Add VDSO version of getcpu 2012-07-11 14:18:40 +10:00
vecemu.c
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vector.S powerpc: Optimise enable_kernel_altivec 2012-04-30 15:37:17 +10:00
vio.c Merge branch 'for-linus-for-3.6-rc1' of git://git.linaro.org/people/mszyprowski/linux-dma-mapping 2012-07-30 10:11:31 -07:00
vmlinux.lds.S powerpc: Remove legacy iSeries bits from assembly files 2012-03-09 10:54:59 +11:00