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The bucket expiry time is the effective expriy time of timers and is greater than or equal to the requested timer expiry time. This is due to the guarantee that timers never expire early and the reduced expiry granularity in the secondary wheel levels. When a timer is enqueued, trigger_dyntick_cpu() checks whether the timer is the new first timer. This check compares next_expiry with the requested timer expiry value and not with the effective expiry value of the bucket into which the timer was queued. Storing the requested timer expiry value in base->next_expiry can lead to base->clk going backwards if the requested timer expiry value is smaller than base->clk. Commit30c66fc30e("timer: Prevent base->clk from moving backward") worked around this by preventing the store when timer->expiry is before base->clk, but did not fix the underlying problem. Use the expiry value of the bucket into which the timer is queued to do the new first timer check. This fixes the base->clk going backward problem. The workaround of commit30c66fc30e("timer: Prevent base->clk from moving backward") in trigger_dyntick_cpu() is not longer necessary as the timers bucket expiry is guaranteed to be greater than or equal base->clk. Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20200717140551.29076-4-frederic@kernel.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.