Commit 294b2711 authored by Anton Vorontsov's avatar Anton Vorontsov Committed by Greg Kroah-Hartman

staging: android/lowmemorykiller: Don't grab tasklist_lock

Grabbing tasklist_lock has its disadvantages, i.e. it blocks
process creation and destruction. If there are lots of processes,
blocking doesn't sound as a great idea.

For LMK, it is sufficient to surround tasks list traverse with
rcu_read_{,un}lock().

>From now on using force_sig() is not safe, as it can race with an
already exiting task, so we use send_sig() now. As a downside, it
won't kill PID namespace init processes, but that's not what we
want anyway.
Suggested-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarAnton Vorontsov <anton.vorontsov@linaro.org>
Reviewed-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 350a1955
...@@ -34,6 +34,7 @@ ...@@ -34,6 +34,7 @@
#include <linux/mm.h> #include <linux/mm.h>
#include <linux/oom.h> #include <linux/oom.h>
#include <linux/sched.h> #include <linux/sched.h>
#include <linux/rcupdate.h>
#include <linux/profile.h> #include <linux/profile.h>
#include <linux/notifier.h> #include <linux/notifier.h>
...@@ -132,7 +133,7 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc) ...@@ -132,7 +133,7 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
} }
selected_oom_adj = min_adj; selected_oom_adj = min_adj;
read_lock(&tasklist_lock); rcu_read_lock();
for_each_process(p) { for_each_process(p) {
struct mm_struct *mm; struct mm_struct *mm;
struct signal_struct *sig; struct signal_struct *sig;
...@@ -180,12 +181,12 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc) ...@@ -180,12 +181,12 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
lowmem_deathpending = selected; lowmem_deathpending = selected;
task_handoff_register(&task_nb); task_handoff_register(&task_nb);
#endif #endif
force_sig(SIGKILL, selected); send_sig(SIGKILL, selected, 0);
rem -= selected_tasksize; rem -= selected_tasksize;
} }
lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n", lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",
sc->nr_to_scan, sc->gfp_mask, rem); sc->nr_to_scan, sc->gfp_mask, rem);
read_unlock(&tasklist_lock); rcu_read_unlock();
return rem; return rem;
} }
......
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