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Commit 2e336b1d authored by John Reck's avatar John Reck
Browse files

Fix access check 

Fixes a bug where USE_CPUSET used access(F_OK)
as a sign that it should try writing to the cpuset
path. It needs to instead use access(W_OK) to
ensure that it has write access as that's what
it would try to open() with.

And stop trying to repeatedly open a file that
doesn't exist.

Change-Id: Ib391ee6f08345051c48a986a732eda30143cb614
parent 091b6319

libcutils/sched_policy.c

+10 −3
Original line number Diff line number Diff line
@@ -52,6 +52,7 @@ static inline SchedPolicy _policy(SchedPolicy p) 
static pthread_once_t the_once = PTHREAD_ONCE_INIT;



static int __sys_supports_schedgroups = -1;

static int __sys_supports_timerslack = -1;



// File descriptors open to /dev/cpuctl/../tasks, setup by initialize, or -1 on error.

static int bg_cgroup_fd = -1;
@@ -104,7 +105,7 @@ static int add_tid_to_cgroup(int tid, int fd) 


static void __initialize(void) {

    char* filename;

    if (!access("/dev/cpuctl/tasks", F_OK)) {

    if (!access("/dev/cpuctl/tasks", W_OK)) {

        __sys_supports_schedgroups = 1;



        filename = "/dev/cpuctl/tasks";
@@ -123,7 +124,7 @@ static void __initialize(void) { 
    }



#ifdef USE_CPUSETS

    if (!access("/dev/cpuset/tasks", F_OK)) {

    if (!access("/dev/cpuset/tasks", W_OK)) {



        filename = "/dev/cpuset/foreground/tasks";

        fg_cpuset_fd = open(filename, O_WRONLY | O_CLOEXEC);
@@ -142,6 +143,10 @@ static void __initialize(void) { 
#endif

    }

#endif



    char buf[64];

    snprintf(buf, sizeof(buf), "/proc/%d/timerslack_ns", getpid());

    __sys_supports_timerslack = !access(buf, W_OK);

}



/*
@@ -417,8 +422,10 @@ int set_sched_policy(int tid, SchedPolicy policy) 
                           &param);

    }



    if (__sys_supports_timerslack) {

        set_timerslack_ns(tid, policy == SP_BACKGROUND ?

                               TIMER_SLACK_BG : TIMER_SLACK_FG);

    }



    return 0;

}