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ANDROID: fs/proc: Perform priority inheritance around access_remote_vm()

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It holds mmap_sem lock which is a hot path. Some debug daemons can end
up holding this lock to get the cmdline of a process, which can result
in slowing down this process.

Add hooks around the calls to allow vendors to implement a simple prio
inheritance scheme to deal with this.

Bug: 344826816
Bug: 289412815
Signed-off-by: Qais Yousef <qyousef@google.com>

(cherry picked from commit b821a3c8fc1efe12782061993b4feef026f8ce58)
[Trivial conflict in include/trace/hooks/sched.h due to new code added.
And in vendor_hooks.c due to code ordering]
Signed-off-by: Qais Yousef <qyousef@google.com>

Change-Id: I160637b30e5bd58d5978b25be8a21ce025175ec3
Signed-off-by: liulu liu <liulu.liu@honor.corp-partner.google.com>
This commit is contained in:
Qais Yousef
2023-07-11 22:37:40 +00:00
committed by Todd Kjos
parent 06a574beb9
commit f3b22c7868
3 changed files with 23 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
fs/proc/base.c
View File

@@ -101,6 +101,7 @@
#include <linux/cpufreq_times.h>
#include <uapi/linux/lsm.h>
#include <trace/events/oom.h>
#include <trace/hooks/sched.h>
#include "internal.h"
#include "fd.h"
@@ -381,13 +382,24 @@ static ssize_t get_task_cmdline(struct task_struct *tsk, char __user *buf,
size_t count, loff_t *pos)
{
struct mm_struct *mm;
bool prio_inherited = false;
int saved_prio;
ssize_t ret;
mm = get_task_mm(tsk);
if (!mm)
return 0;
/*
* access_remote_vm() holds the hot mmap_sem lock which can cause the
* task for which we read cmdline etc for by some debug deamon to slow
* down and suffer a performance hit. Especially if the reader task has
* a low nice value.
*/
trace_android_vh_prio_inheritance(tsk, &saved_prio, &prio_inherited);
ret = get_mm_cmdline(mm, buf, count, pos);
if (prio_inherited)
trace_android_vh_prio_restore(saved_prio);
mmput(mm);
return ret;
}

9
include/trace/hooks/sched.h
View File

@@ -485,6 +485,15 @@ DECLARE_HOOK(android_vh_tick_nohz_idle_stop_tick,
DECLARE_HOOK(android_vh_mmput,
TP_PROTO(struct mm_struct *mm),
TP_ARGS(mm));
DECLARE_HOOK(android_vh_prio_inheritance,
TP_PROTO(struct task_struct *p, int *saved_prio, bool *prio_inherited),
TP_ARGS(p, saved_prio, prio_inherited));
DECLARE_HOOK(android_vh_prio_restore,
TP_PROTO(int saved_prio),
TP_ARGS(saved_prio));
/* macro versions of hooks are no longer required */
#endif /* _TRACE_HOOK_SCHED_H */

2
kernel/sched/vendor_hooks.c
View File

@@ -126,3 +126,5 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_cpu_cgroup_css_alloc);
EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_cpu_cgroup_css_free);
EXPORT_TRACEPOINT_SYMBOL_GPL(android_rvh_dequeue_entity_delayed);
EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_mmput);
EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_prio_inheritance);
EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_prio_restore);