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23 October 2021, 00:29:24 UTC
Revision 28557cc106e6d2aa8b8c5c7687ea9f8055ff3911 authored by Sebastian Andrzej Siewior on 28 June 2018, 06:26:05 UTC, committed by Linus Torvalds on 28 June 2018, 18:16:44 UTC 
Revert mm/vmstat.c: fix vmstat_update() preemption BUG
 
Revert commit c7f26ccfb2c3 ("mm/vmstat.c: fix vmstat_update() preemption
BUG").  Steven saw a "using smp_processor_id() in preemptible" message
and added a preempt_disable() section around it to keep it quiet.  This
is not the right thing to do it does not fix the real problem.

vmstat_update() is invoked by a kworker on a specific CPU.  This worker
it bound to this CPU.  The name of the worker was "kworker/1:1" so it
should have been a worker which was bound to CPU1.  A worker which can
run on any CPU would have a `u' before the first digit.

smp_processor_id() can be used in a preempt-enabled region as long as
the task is bound to a single CPU which is the case here.  If it could
run on an arbitrary CPU then this is the problem we have an should seek
to resolve.

Not only this smp_processor_id() must not be migrated to another CPU but
also refresh_cpu_vm_stats() which might access wrong per-CPU variables.
Not to mention that other code relies on the fact that such a worker
runs on one specific CPU only.

Therefore revert that commit and we should look instead what broke the
affinity mask of the kworker.

Link: http://lkml.kernel.org/r/20180504104451.20278-1-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Steven J. Hill <steven.hill@cavium.com>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 4bb6e96
Raw File
Tip revision: 28557cc106e6d2aa8b8c5c7687ea9f8055ff3911 authored by Sebastian Andrzej Siewior on 28 June 2018, 06:26:05 UTC
Revert mm/vmstat.c: fix vmstat_update() preemption BUG
Tip revision: 28557cc
Makefile.clean 
# SPDX-License-Identifier: GPL-2.0
# ==========================================================================
# Cleaning up
# ==========================================================================

src := $(obj)

PHONY := __clean
__clean:

include scripts/Kbuild.include

# The filename Kbuild has precedence over Makefile
kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
include $(if $(wildcard $(kbuild-dir)/Kbuild), $(kbuild-dir)/Kbuild, $(kbuild-dir)/Makefile)

# Figure out what we need to build from the various variables
# ==========================================================================

__subdir-y	:= $(patsubst %/,%,$(filter %/, $(obj-y)))
subdir-y	+= $(__subdir-y)
__subdir-m	:= $(patsubst %/,%,$(filter %/, $(obj-m)))
subdir-m	+= $(__subdir-m)
__subdir-	:= $(patsubst %/,%,$(filter %/, $(obj-)))
subdir-		+= $(__subdir-)

# Subdirectories we need to descend into

subdir-ym	:= $(sort $(subdir-y) $(subdir-m))
subdir-ymn      := $(sort $(subdir-ym) $(subdir-))

# Add subdir path

subdir-ymn	:= $(addprefix $(obj)/,$(subdir-ymn))

# build a list of files to remove, usually relative to the current
# directory

__clean-files	:= $(extra-y) $(extra-m) $(extra-)       \
		   $(always) $(targets) $(clean-files)   \
		   $(host-progs)                         \
		   $(hostprogs-y) $(hostprogs-m) $(hostprogs-) \
		   $(hostlibs-y) $(hostlibs-m) $(hostlibs-) \
		   $(hostcxxlibs-y) $(hostcxxlibs-m)

__clean-files   := $(filter-out $(no-clean-files), $(__clean-files))

# clean-files is given relative to the current directory, unless it
# starts with $(objtree)/ (which means "./", so do not add "./" unless
# you want to delete a file from the toplevel object directory).

__clean-files   := $(wildcard                                               \
		   $(addprefix $(obj)/, $(filter-out $(objtree)/%, $(__clean-files))) \
		   $(filter $(objtree)/%, $(__clean-files)))

# same as clean-files

__clean-dirs    := $(wildcard                                               \
		   $(addprefix $(obj)/, $(filter-out $(objtree)/%, $(clean-dirs)))    \
		   $(filter $(objtree)/%, $(clean-dirs)))

# ==========================================================================

quiet_cmd_clean    = CLEAN   $(obj)
      cmd_clean    = rm -f $(__clean-files)
quiet_cmd_cleandir = CLEAN   $(__clean-dirs)
      cmd_cleandir = rm -rf $(__clean-dirs)


__clean: $(subdir-ymn)
ifneq ($(strip $(__clean-files)),)
	+$(call cmd,clean)
endif
ifneq ($(strip $(__clean-dirs)),)
	+$(call cmd,cleandir)
endif
	@:


# ===========================================================================
# Generic stuff
# ===========================================================================

# Descending
# ---------------------------------------------------------------------------

PHONY += $(subdir-ymn)
$(subdir-ymn):
	$(Q)$(MAKE) $(clean)=$@

# Declare the contents of the .PHONY variable as phony.  We keep that
# information in a variable se we can use it in if_changed and friends.

.PHONY: $(PHONY)
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