[uml-devel] negative pid -516 possible ?

Toralf Förster

author

2013-12-21 14:36 UTC #0 lore raw

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Trinity'ing a 32 bit linux user mode linux (still the raid x tree issue ....) gives for a guest :

tfoerste@n22 ~ $ date; sudo gdb /home/tfoerste/devel/linux/linux 10044 -n -batch -ex 'bt full' Sat Dec 21 15:33:03 CET 2013
0xb7710424 in __kernel_vsyscall ()
#0 0xb7710424 in __kernel_vsyscall ()
No symbol table info available.
#1 0x083d5d2f in __nanosleep_nocancel ()
No symbol table info available.
#2 0x0807267c in idle_sleep (nsecs=602496466104653440) at arch/um/os-Linux/time.c:183

        ts = {tv_sec = 0, tv_nsec = 6471789}

#3 0x0805fc0f in arch_cpu_idle () at arch/um/kernel/process.c:208 No locals.
#4 0x080a8981 in cpu_idle_loop () at kernel/cpu/idle.c:98 No locals.
#5 cpu_startup_entry (state=CPUHP_ONLINE) at kernel/cpu/idle.c:140 No locals.
#6 0x08421d02 in rest_init () at init/main.c:401

        pid = -516
#7  0x080487e1 in start_kernel () at init/main.c:655
        command_line = 0x85b6400 <command_line> "earlyprintk ubda=/home/tfoerste/virtual/uml/trinity ubdb=/mnt/ramdisk/trinity_swap eth0=tuntap,tap0,72:ef:3d:9f:c3:5a mem=1025M con0=fd:0,fd:1 con=pts rootfstype=ext4  root=98:0"
#8  0x08049e09 in start_kernel_proc (unused=0x0) at arch/um/kernel/skas/process.c:46
        pid = -516
#9  0x0805f7cb in new_thread_handler () at arch/um/kernel/process.c:129
        fn = 0x0

#10 0x00000000 in ?? ()
No symbol table info available.

Is this a valid number ?

- --
MfG/Sincerely
Toralf Förster
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Toralf Förster

author

2013-12-29 12:53 UTC #1 lore raw

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Quoted 25 lines · Toralf Förster

Trinity'ing a 32 bit linux user mode linux (still the raid x tree issue ....) gives for a guest :
tfoerste@n22 ~ $ date; sudo gdb /home/tfoerste/devel/linux/linux 10044 -n -batch -ex 'bt full' Sat Dec 21 15:33:03 CET 2013
0xb7710424 in __kernel_vsyscall ()
#0 0xb7710424 in __kernel_vsyscall ()
No symbol table info available.
#1 0x083d5d2f in __nanosleep_nocancel ()
No symbol table info available.
#2 0x0807267c in idle_sleep (nsecs=602496466104653440) at arch/um/os-Linux/time.c:183
        ts = {tv_sec = 0, tv_nsec = 6471789}
#3 0x0805fc0f in arch_cpu_idle () at arch/um/kernel/process.c:208 No locals.
#4 0x080a8981 in cpu_idle_loop () at kernel/cpu/idle.c:98 No locals.
#5 cpu_startup_entry (state=CPUHP_ONLINE) at kernel/cpu/idle.c:140 No locals.
#6 0x08421d02 in rest_init () at init/main.c:401
        pid = -516
#7  0x080487e1 in start_kernel () at init/main.c:655
        command_line = 0x85b6400 <command_line> "earlyprintk ubda=/home/tfoerste/virtual/uml/trinity ubdb=/mnt/ramdisk/trinity_swap eth0=tuntap,tap0,72:ef:3d:9f:c3:5a mem=1025M con0=fd:0,fd:1 con=pts rootfstype=ext4  root=98:0"
#8  0x08049e09 in start_kernel_proc (unused=0x0) at arch/um/kernel/skas/process.c:46
        pid = -516
#9  0x0805f7cb in new_thread_handler () at arch/um/kernel/process.c:129
        fn = 0x0

Quoted 7 lines

#10 0x00000000 in ?? ()
No symbol table info available.
Is this a valid number ?

I'm asking b/c there's no process group id 516, and -516 always happens in the back traces. And furthermore after a while the UML system does no longer serve any ssh login attempts.

- --
MfG/Sincerely
Toralf Förster
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[email protected]

2013-12-29 13:17 UTC #2 lore raw

Quoted 17 lines

Quoted 17 lines
#6 0x08421d02 in rest_init () at init/main.c:401
        pid = -516
#7  0x080487e1 in start_kernel () at init/main.c:655
        command_line = 0x85b6400 <command_line> "earlyprintk 
ubda=/home/tfoerste/virtual/uml/trinity ubdb=/mnt/ramdisk/trinity_swap eth0=tuntap,tap0,72:ef:3d:9f:c3:5a mem=1025M con0=fd:0,fd:1 con=pts rootfstype=ext4 root=98:0"
#8 0x08049e09 in start_kernel_proc (unused=0x0) at arch/um/kernel/skas/process.c:46
        pid = -516
#9  0x0805f7cb in new_thread_handler () at 
arch/um/kernel/process.c:129
        fn = 0x0
#10 0x00000000 in ?? ()
No symbol table info available.

Quoted 5 lines

Quoted 1 line
Is this a valid number ?
I'm asking b/c there's no process group id 516, and -516 always happens in the back traces.
And furthermore after a while the UML system does no longer serve any ssh login attempts.

516 == -ERESTART_RESTARTBLOCK ??

Stian

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Richard Weinberger

2014-01-02 13:38 UTC #3 lore raw

Quoted 17 lines · On Sun, Dec 29, 2013 at 2:14 PM, <[email protected]> wrote:

Quoted 17 lines
Quoted 17 lines
#6 0x08421d02 in rest_init () at init/main.c:401
        pid = -516
#7  0x080487e1 in start_kernel () at init/main.c:655
        command_line = 0x85b6400 <command_line> "earlyprintk
ubda=/home/tfoerste/virtual/uml/trinity ubdb=/mnt/ramdisk/trinity_swap eth0=tuntap,tap0,72:ef:3d:9f:c3:5a mem=1025M con0=fd:0,fd:1 con=pts rootfstype=ext4 root=98:0"
#8 0x08049e09 in start_kernel_proc (unused=0x0) at arch/um/kernel/skas/process.c:46
        pid = -516
#9  0x0805f7cb in new_thread_handler () at
arch/um/kernel/process.c:129
        fn = 0x0
#10 0x00000000 in ?? ()
No symbol table info available.

Quoted 7 lines

Quoted 5 lines
Quoted 1 line
Is this a valid number ?
I'm asking b/c there's no process group id 516, and -516 always happens in the back traces.
And furthermore after a while the UML system does no longer serve any ssh login attempts.
516 == -ERESTART_RESTARTBLOCK ??

Yeah, maybe.

Toralf, where exactly comes this back trace from? "gives for a guest" is not a good error description.
Did it crash and you took it from the core dump?
Did it panic() and you attached to it?
Did it hang...?
IOW don't throw random back traces to us without much details. ;-)

The number -516 is a bit odd because you see it in arch/um/kernel/skas/process.c.
In that function it comes from os_getpid() which indicates that the host kernel reports that number.
...very strange.

init/main.c makes a bit more sense. Maybe a kthread creation within UML returned that internal error.

Can you try the attached debug patch?
If the BUG_ON() trigger, please show us panic from UML, not just the gdb back trace.

Signature · 2 lines

Thanks,
//richard

arch/um/kernel/skas/process.c +2 -0

index 4da11b3..71a5828 100644
@@ -38,6 +38,8 @@ static int __init start_kernel_proc(void *unused)
 	block_signals();
 	pid = os_getpid();
 
+	BUG_ON(pid == -516);
+
 	cpu_tasks[0].pid = pid;
 	cpu_tasks[0].task = current;
 #ifdef CONFIG_SMP

init/main.c +1 -0

index febc511..9ad68ab 100644
@@ -386,6 +386,7 @@ static noinline void __init_refok rest_init(void)
 	kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
 	numa_default_policy();
 	pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
+	BUG_ON(pid == -516);
 	rcu_read_lock();
 	kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
 	rcu_read_unlock();

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