[FIX] race condition on probes disarming (at stop)

As a workaround we shut down all CPUs except for the boot one and keep
the cpu_add_remove_lock held until we are done.

Change-Id: I4da16240d963a0cdbdd8b0be0507c6941c41ee69
Signed-off-by: Vasiliy Ulyanov <v.ulyanov@samsung.com>

diff --git a/parser/swap_msg_parser.c b/parser/swap_msg_parser.c
index e374bf6..aac3455 100644 (file)
--- a/parser/swap_msg_parser.c
+++ b/parser/swap_msg_parser.c
@@ -25,6 +25,8 @@
 
 #include <linux/module.h>
 #include <linux/vmalloc.h>
+#include <linux/cpumask.h>
+#include <linux/cpu.h>
 #include <asm/uaccess.h>
 
 #include "parser_defs.h"
@@ -33,6 +35,7 @@
 
 #include <driver/driver_to_msg.h>
 #include <driver/swap_ioctl.h>
+#include <ksyms/ksyms.h>
 
 enum MSG_ID {
        MSG_KEEP_ALIVE          = 0x0001,
@@ -48,6 +51,82 @@ struct basic_msg_fmt {
        u32 len;
 } __attribute__((packed));
 
+static void (*swap_cpu_maps_update_begin)(void);
+static void (*swap_cpu_maps_update_done)(void);
+static int (*swap_cpu_down)(unsigned int, int);
+static int (*swap_cpu_up)(unsigned int, int);
+
+static int init_cpu_deps(void)
+{
+       const char *sym = "cpu_maps_update_begin";
+
+       swap_cpu_maps_update_begin = (void *)swap_ksyms(sym);
+       if (!swap_cpu_maps_update_begin)
+               goto not_found;
+
+       sym = "cpu_maps_update_done";
+       swap_cpu_maps_update_done = (void *)swap_ksyms(sym);
+       if (!swap_cpu_maps_update_done)
+               goto not_found;
+
+       sym = "_cpu_up";
+       swap_cpu_up = (void *)swap_ksyms(sym);
+       if (!swap_cpu_up)
+               goto not_found;
+
+       sym = "_cpu_down";
+       swap_cpu_down = (void *)swap_ksyms(sym);
+       if (!swap_cpu_down)
+               goto not_found;
+
+       return 0;
+
+not_found:
+       printk("ERROR: symbol %s(...) not found\n", sym);
+       return -ESRCH;
+}
+
+static int swap_disable_nonboot_cpus_lock(struct cpumask *mask)
+{
+       int boot_cpu, cpu;
+       int ret = 0;
+
+       swap_cpu_maps_update_begin();
+       cpumask_clear(mask);
+
+       boot_cpu = cpumask_first(cpu_online_mask);
+
+       for_each_online_cpu(cpu) {
+               if (cpu == boot_cpu)
+                       continue;
+               ret = swap_cpu_down(cpu, 0);
+               if (ret == 0)
+                       cpumask_set_cpu(cpu, mask);
+               printk("===> SWAP CPU[%d] down(%d)\n", cpu, ret);
+       }
+
+       WARN_ON(num_online_cpus() > 1);
+       return ret;
+}
+
+static int swap_enable_nonboot_cpus_unlock(struct cpumask *mask)
+{
+       int cpu, ret = 0;
+
+       if (cpumask_empty(mask))
+               goto out;
+
+       for_each_cpu(cpu, mask) {
+               ret = swap_cpu_up(cpu, 0);
+               printk("===> SWAP CPU[%d] up(%d)\n", cpu, ret);
+       }
+
+       swap_cpu_maps_update_done();
+
+out:
+       return ret;
+}
+
 static int msg_handler(void __user *msg)
 {
        int ret;
@@ -89,10 +168,17 @@ static int msg_handler(void __user *msg)
                print_parse_debug("MSG_START. size=%d\n", size);
                ret = msg_start(&mb);
                break;
-       case MSG_STOP:
+       case MSG_STOP: {
+               struct cpumask mask;
+
                print_parse_debug("MSG_STOP. size=%d\n", size);
+
+               swap_disable_nonboot_cpus_lock(&mask);
                ret = msg_stop(&mb);
+               swap_enable_nonboot_cpus_unlock(&mask);
+
                break;
+       }
        case MSG_CONFIG:
                print_parse_debug("MSG_CONFIG. size=%d\n", size);
                ret = msg_config(&mb);
@@ -129,10 +215,16 @@ static void unregister_msg_handler(void)
 static int __init swap_parser_init(void)
 {
        int ret;
+
+       ret = init_cpu_deps();
+       if (ret)
+               goto out;
+
        register_msg_handler();
 
        ret = init_cmd();
 
+out:
        return ret;
 }