77c12fc959
In preparation for the buddy hardlockup detector where the CPU checking for lockup might not be the currently running CPU, add a "cpu" parameter to watchdog_hardlockup_check(). As part of this change, make hrtimer_interrupts an atomic_t since now the CPU incrementing the value and the CPU reading the value might be different. Technially this could also be done with just READ_ONCE and WRITE_ONCE, but atomic_t feels a little cleaner in this case. While hrtimer_interrupts is made atomic_t, we change hrtimer_interrupts_saved from "unsigned long" to "int". The "int" is needed to match the data type backing atomic_t for hrtimer_interrupts. Even if this changes us from 64-bits to 32-bits (which I don't think is true for most compilers), it doesn't really matter. All we ever do is increment it every few seconds and compare it to an old value so 32-bits is fine (even 16-bits would be). The "signed" vs "unsigned" also doesn't matter for simple equality comparisons. hrtimer_interrupts_saved is _not_ switched to atomic_t nor even accessed with READ_ONCE / WRITE_ONCE. The hrtimer_interrupts_saved is always consistently accessed with the same CPU. NOTE: with the upcoming "buddy" detector there is one special case. When a CPU goes offline/online then we can change which CPU is the one to consistently access a given instance of hrtimer_interrupts_saved. We still can't end up with a partially updated hrtimer_interrupts_saved, however, because we end up petting all affected CPUs to make sure the new and old CPU can't end up somehow read/write hrtimer_interrupts_saved at the same time. Link: https://lkml.kernel.org/r/20230519101840.v5.10.I3a7d4dd8c23ac30ee0b607d77feb6646b64825c0@changeid Signed-off-by: Douglas Anderson <dianders@chromium.org> Cc: Andi Kleen <ak@linux.intel.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Chen-Yu Tsai <wens@csie.org> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: Colin Cross <ccross@android.com> Cc: Daniel Thompson <daniel.thompson@linaro.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Guenter Roeck <groeck@chromium.org> Cc: Ian Rogers <irogers@google.com> Cc: Lecopzer Chen <lecopzer.chen@mediatek.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Masayoshi Mizuma <msys.mizuma@gmail.com> Cc: Matthias Kaehlcke <mka@chromium.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Petr Mladek <pmladek@suse.com> Cc: Pingfan Liu <kernelfans@gmail.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com> Cc: Ricardo Neri <ricardo.neri@intel.com> Cc: Stephane Eranian <eranian@google.com> Cc: Stephen Boyd <swboyd@chromium.org> Cc: Sumit Garg <sumit.garg@linaro.org> Cc: Tzung-Bi Shih <tzungbi@chromium.org> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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.