On 26/02/2019 12:06, Dave Martin wrote:

On Thu, Feb 21, 2019 at 12:39:39PM +0000, Julien Grall wrote:

quoted

Hi Dave,

On 18/02/2019 19:52, Dave Martin wrote:

quoted

This patch updates fpsimd_flush_task_state() to mirror the new
semantics of fpsimd_flush_cpu_state() introduced by commit
d8ad71fa38a9 ("arm64: fpsimd: Fix TIF_FOREIGN_FPSTATE after
invalidating cpu regs").  Both functions now implicitly set

NIT: Double-space before "Both"

quoted

TIF_FOREIGN_FPSTATE to indicate that the task's FPSIMD state is not
loaded into the cpu.

As a side-effect, fpsimd_flush_task_state() now sets
TIF_FOREIGN_FPSTATE even for non-running tasks.  In the case of

NIT: Double sppace before "In".

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non-running tasks this is not useful but also harmless, because the
flag is live only while the corresponding task is running.  This
function is not called from fast paths, so special-casing this for
the task == current case is not really worth it.

Compiler barriers previously present in restore_sve_fpsimd_context()
are pulled into fpsimd_flush_task_state() so that it can be safely
called with preemption enabled if necessary.

Explicit calls to set TIF_FOREIGN_FPSTATE that accompany
fpsimd_flush_task_state() calls and are now redundant are removed
as appropriate.

fpsimd_flush_task_state() is used to get exclusive access to the
representation of the task's state via task_struct, for the purpose
of replacing the state.  Thus, the call to this function should

NIT: Double-space before "Thus".

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happen before manipulating fpsimd_state or sve_state etc. in
task_struct.  Anomalous cases are reordered appropriately in order

NIT: Double-space before "Anomalous".

A habit rather than a mistake [1], and I don't propose to change it ;)

I wasn't aware of this. Thank you for the pointer! Please ignore the comments on 
it :).


Cheers,

-- 
Julien Grall

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