Re: Printing thread_local a.k.a. __thread variables

On 02/12/2018 05:54 PM, Yao Qi wrote:

> ... is it broken in every threads in "thread apply all" or just in some
> threads?  Can you reproduce it every time or it is intermittent?
> If you manually switch threads via command "thread N", can
> you examine 'tlocal'?

It seems that 'qGetTLSAddr' fails every time for any thread in question:

(gdb) info threads
   Id   Target Id         Frame
* 1    Thread 19378.19378 "t-thread" 0x00007f62ae10b89d in pthread_join () from target:/lib64/libpthread.so.0
   2    Thread 19378.19379 "worker" 0x00007f62ae11499d in nanosleep () from target:/lib64/libpthread.so.0
   3    Thread 19378.19380 "worker" 0x00007f62ae11499d in nanosleep () from target:/lib64/libpthread.so.0
   4    Thread 19378.19381 "worker" 0x00007f62ae11499d in nanosleep () from target:/lib64/libpthread.so.0
   5    Thread 19378.19382 "worker" 0x00007f62ae11499d in nanosleep () from target:/lib64/libpthread.so.0
   6    Thread 19378.19383 "worker" 0x00007f62ae11499d in nanosleep () from target:/lib64/libpthread.so.0
   7    Thread 19378.19384 "worker" 0x00007f62ae11499d in nanosleep () from target:/lib64/libpthread.so.0
   8    Thread 19378.19385 "worker" 0x00007f62ae11499d in nanosleep () from target:/lib64/libpthread.so.0
   9    Thread 19378.19386 "worker" 0x00007f62ae11499d in nanosleep () from target:/lib64/libpthread.so.0
(gdb) print tlocal
Cannot find thread-local storage for Thread 19378.19378, executable file target:/home/dantipov/tmp/t-thread:
Remote target failed to process qGetTLSAddr request
(gdb) thread 2
[Switching to thread 2 (Thread 19378.19379)]
#0  0x00007f62ae11499d in nanosleep () from target:/lib64/libpthread.so.0
(gdb) print tlocal
Cannot find thread-local storage for Thread 19378.19379, executable file target:/home/dantipov/tmp/t-thread:
Remote target failed to process qGetTLSAddr request
(gdb) thread 3
[Switching to thread 3 (Thread 19378.19380)]
#0  0x00007f62ae11499d in nanosleep () from target:/lib64/libpthread.so.0
(gdb) print tlocal
Cannot find thread-local storage for Thread 19378.19380, executable file target:/home/dantipov/tmp/t-thread:
Remote target failed to process qGetTLSAddr request

gdbserver output is:
...
getpkt ("qGetTLSAddr:p4bb2.4bb2,0,7f62aedff330");  [no ack sent]
putpkt ("$E01#a6"); [noack mode]
...
getpkt ("qGetTLSAddr:p4bb2.4bb3,0,7f62aedff330");  [no ack sent]
putpkt ("$E01#a6"); [noack mode]
...
getpkt ("qGetTLSAddr:p4bb2.4bb4,0,7f62aedff330");  [no ack sent]
putpkt ("$E01#a6"); [noack mode]
...

As for the local debugging, the same GDB binary on the same system works as expected:

(gdb) i thr
   Id   Target Id         Frame
* 1    Thread 0x7f62aedd2740 (LWP 19378) "t-thread" 0x00007f62ae10b89d in pthread_join () from /lib64/libpthread.so.0
   2    Thread 0x7f62add2d700 (LWP 19379) "worker" 0x00007f62ae11499d in nanosleep () from /lib64/libpthread.so.0
   3    Thread 0x7f62ad52c700 (LWP 19380) "worker" 0x00007f62ae11499d in nanosleep () from /lib64/libpthread.so.0
   4    Thread 0x7f62acd2b700 (LWP 19381) "worker" 0x00007f62ae11499d in nanosleep () from /lib64/libpthread.so.0
   5    Thread 0x7f62ac52a700 (LWP 19382) "worker" 0x00007f62ae11499d in nanosleep () from /lib64/libpthread.so.0
   6    Thread 0x7f62abd29700 (LWP 19383) "worker" 0x00007f62ae11499d in nanosleep () from /lib64/libpthread.so.0
   7    Thread 0x7f62ab528700 (LWP 19384) "worker" 0x00007f62ae11499d in nanosleep () from /lib64/libpthread.so.0
   8    Thread 0x7f62aad27700 (LWP 19385) "worker" 0x00007f62ae11499d in nanosleep () from /lib64/libpthread.so.0
   9    Thread 0x7f62aa526700 (LWP 19386) "worker" 0x00007f62ae11499d in nanosleep () from /lib64/libpthread.so.0
(gdb) print tlocal
$1 = 100
(gdb) thread 2
[Switching to thread 2 (Thread 0x7f62add2d700 (LWP 19379))]
#0  0x00007f62ae11499d in nanosleep () from /lib64/libpthread.so.0
(gdb) print tlocal
$2 = 653
(gdb) thread 3
[Switching to thread 3 (Thread 0x7f62ad52c700 (LWP 19380))]
#0  0x00007f62ae11499d in nanosleep () from /lib64/libpthread.so.0
(gdb) print tlocal
$3 = 1220

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