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Commit 0e4add4a authored by Hillf Danton's avatar Hillf Danton Committed by Will Deacon
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arm64: assembler: Update comment above cond_yield_neon() macro 



Since commit 7faa313f ("arm64: preempt: Fix big-endian when checking
preempt count in assembly") both the preempt count and the 'need_resched'
flag are checked as part of a single 64-bit load in cond_yield_neon(),
so update the stale comment to reflect reality.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Dave Martin <Dave.Martin@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarHillf Danton <hdanton@sina.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 14ae42a6

arch/arm64/include/asm/assembler.h

+5 −6
Original line number Diff line number Diff line
@@ -718,12 +718,11 @@ USER(\label, ic ivau, \tmp2) // invalidate I line PoU 
 * the output section, any use of such directives is undefined.

 *

 * The yield itself consists of the following:

 * - Check whether the preempt count is exactly 1, in which case disabling

 *   preemption once will make the task preemptible. If this is not the case,

 *   yielding is pointless.

 * - Check whether TIF_NEED_RESCHED is set, and if so, disable and re-enable

 *   kernel mode NEON (which will trigger a reschedule), and branch to the

 *   yield fixup code.

 * - Check whether the preempt count is exactly 1 and a reschedule is also

 *   needed. If so, calling of preempt_enable() in kernel_neon_end() will

 *   trigger a reschedule. If it is not the case, yielding is pointless.

 * - Disable and re-enable kernel mode NEON, and branch to the yield fixup

 *   code.

 *

 * This macro sequence may clobber all CPU state that is not guaranteed by the

 * AAPCS to be preserved across an ordinary function call.