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Nicholas Piggin 111fe7186b mm: generalise COW SMC TLB flushing race comment
I'm not sure if I'm completely missing something here, but AFAIKS the
reference to the mysterious "COW SMC race" confuses the issue.  The
original changelog and mailing list thread didn't help me either.

This SMC race is where the problem was detected, but isn't the general
problem bigger and more obvious: that the new PTE could be picked up at
any time by any TLB while entries for the old PTE exist in other TLBs
before the TLB flush takes effect?

The case where the iTLB and dTLB of a CPU are pointing at different pages
is an interesting one but follows from the general problem.

The other (minor) thing with the comment I think it makes it a bit clearer
to say what the old code was doing (i.e., it avoids the race as opposed to
what?).

References: 4ce072f1fa ("mm: fix a race condition under SMC + COW")
Link: https://lkml.kernel.org/r/20201215121119.351650-1-npiggin@gmail.com
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suresh Siddha <sbsiddha@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-12-29 15:36:49 -08:00
arch mm: memmap defer init doesn't work as expected 2020-12-29 15:36:49 -08:00
block
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Documentation A small set of late-arriving, small documentation fixes. 2020-12-24 14:20:33 -08:00
drivers Revert WQ_SYSFS change that broke reencryption (and all other 2020-12-28 13:32:16 -08:00
fs proc mountinfo: make splice available again 2020-12-27 12:00:36 -08:00
include mm: memmap defer init doesn't work as expected 2020-12-29 15:36:49 -08:00
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kernel Merge branch 'for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2020-12-28 11:23:02 -08:00
lib kasan: introduce CONFIG_KASAN_HW_TAGS 2020-12-22 12:55:07 -08:00
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mm mm: generalise COW SMC TLB flushing race comment 2020-12-29 15:36:49 -08:00
net
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scripts checkpatch: prefer strscpy to strlcpy 2020-12-29 15:36:49 -08:00
security Provide a fix for the incorrect handling of privilege 2020-12-24 14:08:43 -08:00
sound sound fixes for 5.11-rc1 2020-12-23 15:11:08 -08:00
tools selftests/vm: fix building protection keys test 2020-12-29 15:36:49 -08:00
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MAINTAINERS Misc fixes/updates: 2020-12-27 09:06:10 -08:00
Makefile Linux 5.11-rc1 2020-12-27 15:30:22 -08:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.