/* vi: set sw=4 ts=4: */
/*
 * taskset - retrieve or set a processes' CPU affinity
 * Copyright (c) 2006 Bernhard Reutner-Fischer
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */
//config:config TASKSET
//config:       bool "taskset (4.2 kb)"
//config:       default y
//config:       help
//config:       Retrieve or set a processes's CPU affinity.
//config:       This requires sched_{g,s}etaffinity support in your libc.
//config:
//config:config FEATURE_TASKSET_FANCY
//config:       bool "Fancy output"
//config:       default y
//config:       depends on TASKSET
//config:       help
//config:       Needed for machines with more than 32-64 CPUs:
//config:       affinity parameter 0xHHHHHHHHHHHHHHHHHHHH can be arbitrarily long
//config:       in this case. Otherwise, it is limited to sizeof(long).

//applet:IF_TASKSET(APPLET_NOEXEC(taskset, taskset, BB_DIR_USR_BIN, BB_SUID_DROP, taskset))

//kbuild:lib-$(CONFIG_TASKSET) += taskset.o

//usage:#define taskset_trivial_usage
//usage:       "[-p] [HEXMASK] PID | PROG ARGS"
//usage:#define taskset_full_usage "\n\n"
//usage:       "Set or get CPU affinity\n"
//usage:     "\n        -p      Operate on an existing PID"
//usage:
//usage:#define taskset_example_usage
//usage:       "$ taskset 0x7 ./dgemm_test&\n"
//usage:       "$ taskset -p 0x1 $!\n"
//usage:       "pid 4790's current affinity mask: 7\n"
//usage:       "pid 4790's new affinity mask: 1\n"
//usage:       "$ taskset 0x7 /bin/sh -c './taskset -p 0x1 $$'\n"
//usage:       "pid 6671's current affinity mask: 1\n"
//usage:       "pid 6671's new affinity mask: 1\n"
//usage:       "$ taskset -p 1\n"
//usage:       "pid 1's current affinity mask: 3\n"
/*
 * Not yet implemented:
 * -a/--all-tasks (affect all threads)
 *      needs to get TIDs from /proc/PID/task/ and use _them_ as "pid" in sched_setaffinity(pid)
 * -c/--cpu-list  (specify CPUs via "1,3,5-7")
 */

#include <sched.h>
#include "libbb.h"

typedef unsigned long ul;
#define SZOF_UL (unsigned)(sizeof(ul))
#define BITS_UL (unsigned)(sizeof(ul)*8)
#define MASK_UL (unsigned)(sizeof(ul)*8 - 1)

#if ENABLE_FEATURE_TASKSET_FANCY
#define TASKSET_PRINTF_MASK "%s"
/* craft a string from the mask */
static char *from_mask(const ul *mask, unsigned sz_in_bytes)
{
        char *str = xzalloc((sz_in_bytes+1) * 2); /* we will leak it */
        char *p = str;
        for (;;) {
                ul v = *mask++;
                if (SZOF_UL == 4)
                        p += sprintf(p, "%08lx", v);
                if (SZOF_UL == 8)
                        p += sprintf(p, "%016lx", v);
                if (SZOF_UL == 16)
                        p += sprintf(p, "%032lx", v); /* :) */
                sz_in_bytes -= SZOF_UL;
                if ((int)sz_in_bytes <= 0)
                        break;
        }
        while (str[0] == '0' && str[1])
                str++;
        return str;
}
#else
#define TASKSET_PRINTF_MASK "%lx"
static unsigned long long from_mask(ul *mask, unsigned sz_in_bytes UNUSED_PARAM)
{
        return *mask;
}
#endif

static unsigned long *get_aff(int pid, unsigned *sz)
{
        int r;
        unsigned long *mask = NULL;
        unsigned sz_in_bytes = *sz;

        for (;;) {
                mask = xrealloc(mask, sz_in_bytes);
                r = sched_getaffinity(pid, sz_in_bytes, (void*)mask);
                if (r == 0)
                        break;
                sz_in_bytes *= 2;
                if (errno == EINVAL && (int)sz_in_bytes > 0)
                        continue;
                bb_perror_msg_and_die("can't %cet pid %d's affinity", 'g', pid);
        }
        //bb_error_msg("get mask[0]:%lx sz_in_bytes:%d", mask[0], sz_in_bytes);
        *sz = sz_in_bytes;
        return mask;
}

int taskset_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int taskset_main(int argc UNUSED_PARAM, char **argv)
{
        ul *mask;
        unsigned mask_size_in_bytes;
        pid_t pid = 0;
        unsigned opt_p;
        const char *current_new;
        char *aff;

        /* NB: we mimic util-linux's taskset: -p does not take
         * an argument, i.e., "-pN" is NOT valid, only "-p N"!
         * Indeed, util-linux-2.13-pre7 uses:
         * getopt_long(argc, argv, "+pchV", ...), not "...p:..." */

        opt_p = getopt32(argv, "^+" "p" "\0" "-1" /* at least 1 arg */);
        argv += optind;

        aff = *argv++;
        if (opt_p) {
                char *pid_str = aff;
                if (*argv) { /* "-p <aff> <pid> ...rest.is.ignored..." */
                        pid_str = *argv; /* NB: *argv != NULL in this case */
                }
                /* else it was just "-p <pid>", and *argv == NULL */
                pid = xatoul_range(pid_str, 1, ((unsigned)(pid_t)ULONG_MAX) >> 1);
        } else {
                /* <aff> <cmd...> */
                if (!*argv)
                        bb_show_usage();
        }

        mask_size_in_bytes = SZOF_UL;
        current_new = "current";
 print_aff:
        mask = get_aff(pid, &mask_size_in_bytes);
        if (opt_p) {
                printf("pid %d's %s affinity mask: "TASKSET_PRINTF_MASK"\n",
                                pid, current_new, from_mask(mask, mask_size_in_bytes));
                if (*argv == NULL) {
                        /* Either it was just "-p <pid>",
                         * or it was "-p <aff> <pid>" and we came here
                         * for the second time (see goto below) */
                        return EXIT_SUCCESS;
                }
                *argv = NULL;
                current_new = "new";
        }
        memset(mask, 0, mask_size_in_bytes);

        /* Affinity was specified, translate it into mask */
        /* it is always in hex, skip "0x" if it exists */
        if (aff[0] == '0' && (aff[1]|0x20) == 'x')
                aff += 2;

        if (!ENABLE_FEATURE_TASKSET_FANCY) {
                mask[0] = xstrtoul(aff, 16);
        } else {
                unsigned i;
                char *last_char;

                i = 0; /* bit pos in mask[] */

                /* aff is ASCII hex string, accept very long masks in this form.
                 * Process hex string AABBCCDD... to ulong mask[]
                 * from the rightmost nibble, which is least-significant.
                 * Bits not fitting into mask[] are ignored: (example: 1234
                 * in 12340000000000000000000000000000000000000ff)
                 */
                last_char = strchrnul(aff, '\0');
                while (last_char > aff) {
                        char c;
                        ul val;

                        last_char--;
                        c = *last_char;
                        if (isdigit(c))
                                val = c - '0';
                        else if ((c|0x20) >= 'a' && (c|0x20) <= 'f')
                                val = (c|0x20) - ('a' - 10);
                        else
                                bb_error_msg_and_die("bad affinity '%s'", aff);

                        if (i < mask_size_in_bytes * 8) {
                                mask[i / BITS_UL] |= val << (i & MASK_UL);
                                //bb_error_msg("bit %d set", i);
                        }
                        /* else:
                         * We can error out here, but we don't.
                         * For one, kernel itself ignores bits in mask[]
                         * which do not map to any CPUs:
                         * if mask[] has one 32-bit long element,
                         * but you have only 8 CPUs, all bits beyond first 8
                         * are ignored, silently.
                         * No point in making bits past 31th to be errors.
                         */
                        i += 4;
                }
        }

        /* Set pid's or our own (pid==0) affinity */
        if (sched_setaffinity(pid, mask_size_in_bytes, (void*)mask))
                bb_perror_msg_and_die("can't %cet pid %d's affinity", 's', pid);
        //bb_error_msg("set mask[0]:%lx", mask[0]);

        if (!argv[0]) /* "-p <aff> <pid> [...ignored...]" */
                goto print_aff; /* print new affinity and exit */

        BB_EXECVP_or_die(argv);
}