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139d025cda
The current active_mm reference counting is confusing and sub-optimal. Rewrite the code to explicitly consider the 4 separate cases: user -> user When switching between two user tasks, all we need to consider is switch_mm(). user -> kernel When switching from a user task to a kernel task (which doesn't have an associated mm) we retain the last mm in our active_mm. Increment a reference count on active_mm. kernel -> kernel When switching between kernel threads, all we need to do is pass along the active_mm reference. kernel -> user When switching between a kernel and user task, we must switch from the last active_mm to the next mm, hoping of course that these are the same. Decrement a reference on the active_mm. The code keeps a different order, because as you'll note, both 'to user' cases require switch_mm(). And where the old code would increment/decrement for the 'kernel -> kernel' case, the new code observes this is a neutral operation and avoids touching the reference count. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Rik van Riel <riel@surriel.com> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: luto@kernel.org |
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.. | ||
autogroup.c | ||
autogroup.h | ||
clock.c | ||
completion.c | ||
core.c | ||
cpuacct.c | ||
cpudeadline.c | ||
cpudeadline.h | ||
cpufreq_schedutil.c | ||
cpufreq.c | ||
cpupri.c | ||
cpupri.h | ||
cputime.c | ||
deadline.c | ||
debug.c | ||
fair.c | ||
features.h | ||
idle.c | ||
isolation.c | ||
loadavg.c | ||
Makefile | ||
membarrier.c | ||
pelt.c | ||
pelt.h | ||
psi.c | ||
rt.c | ||
sched-pelt.h | ||
sched.h | ||
stats.c | ||
stats.h | ||
stop_task.c | ||
swait.c | ||
topology.c | ||
wait_bit.c | ||
wait.c |