I get a hang like this occasionally: (gdb) bt #0 __lll_lock_wait_private () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:63 #1 0x00007f160c6f927a in __run_fork_handlers (who=(unknown: 209394016), who@entry=atfork_run_prepare) at register-atfork.c:116 #2 0x00007f160c6b7897 in __libc_fork () at ../sysdeps/nptl/fork.c:58 #3 0x00000000004027d6 in sigusr1_handler (signo=<optimized out>) at tst-mallocfork2.c:80 #4 sigusr1_handler (signo=<optimized out>) at tst-mallocfork2.c:64 #5 <signal handler called> #6 0x00007f160c6f92e4 in __run_fork_handlers (who=who@entry=atfork_run_parent) at register-atfork.c:136 #7 0x00007f160c6b79a2 in __libc_fork () at ../sysdeps/nptl/fork.c:152 #8 0x0000000000402567 in do_test () at tst-mallocfork2.c:156 #9 0x0000000000402dd2 in support_test_main (argc=1, argv=0x7ffc81ef1ab0, config=config@entry=0x7ffc81ef1970) at support_test_main.c:350 #10 0x0000000000402362 in main (argc=<optimized out>, argv=<optimized out>) at ../support/test-driver.c:168 We need to extend the lock avoidance to atfork_lock. Potentially introduced by: commit 27761a1042daf01987e7d79636d0c41511c6df3c Author: Adhemerval Zanella <adhemerval.zanella@linaro.org> Date: Thu Feb 1 17:57:56 2018 -0200 Refactor atfork handlers
This is an automated email from the git hooks/post-receive script. It was generated because a ref change was pushed to the repository containing the project "GNU C Library master sources". The branch, master has been updated via 669ff911e2571f74a2668493e326ac9a505776bd (commit) from d0bd87d4c0c11b93f79d1c3531ffb13b4b538190 (commit) Those revisions listed above that are new to this repository have not appeared on any other notification email; so we list those revisions in full, below. - Log ----------------------------------------------------------------- https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=669ff911e2571f74a2668493e326ac9a505776bd commit 669ff911e2571f74a2668493e326ac9a505776bd Author: Florian Weimer <fweimer@redhat.com> Date: Fri Feb 8 12:46:19 2019 +0100 nptl: Avoid fork handler lock for async-signal-safe fork [BZ #24161] Commit 27761a1042daf01987e7d79636d0c41511c6df3c ("Refactor atfork handlers") introduced a lock, atfork_lock, around fork handler list accesses. It turns out that this lock occasionally results in self-deadlocks in malloc/tst-mallocfork2: (gdb) bt #0 __lll_lock_wait_private () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:63 #1 0x00007f160c6f927a in __run_fork_handlers (who=(unknown: 209394016), who@entry=atfork_run_prepare) at register-atfork.c:116 #2 0x00007f160c6b7897 in __libc_fork () at ../sysdeps/nptl/fork.c:58 #3 0x00000000004027d6 in sigusr1_handler (signo=<optimized out>) at tst-mallocfork2.c:80 #4 sigusr1_handler (signo=<optimized out>) at tst-mallocfork2.c:64 #5 <signal handler called> #6 0x00007f160c6f92e4 in __run_fork_handlers (who=who@entry=atfork_run_parent) at register-atfork.c:136 #7 0x00007f160c6b79a2 in __libc_fork () at ../sysdeps/nptl/fork.c:152 #8 0x0000000000402567 in do_test () at tst-mallocfork2.c:156 #9 0x0000000000402dd2 in support_test_main (argc=1, argv=0x7ffc81ef1ab0, config=config@entry=0x7ffc81ef1970) at support_test_main.c:350 #10 0x0000000000402362 in main (argc=<optimized out>, argv=<optimized out>) at ../support/test-driver.c:168 If no locking happens in the single-threaded case (where fork is expected to be async-signal-safe), this deadlock is avoided. (pthread_atfork is not required to be async-signal-safe, so a fork call from a signal handler interrupting pthread_atfork is not a problem.) ----------------------------------------------------------------------- Summary of changes: ChangeLog | 10 ++++++++++ nptl/register-atfork.c | 8 +++++--- sysdeps/nptl/fork.c | 6 +++--- sysdeps/nptl/fork.h | 8 +++++--- 4 files changed, 23 insertions(+), 9 deletions(-)
Fixed in glibc 2.30.
This is an automated email from the git hooks/post-receive script. It was generated because a ref change was pushed to the repository containing the project "GNU C Library master sources". The branch, release/2.28/master has been updated via 60f80624257ef84eacfd9b400bda1b5a5e8e7816 (commit) from a9f60b1571cc7821cd6bc4dbeba12194d484e7f5 (commit) Those revisions listed above that are new to this repository have not appeared on any other notification email; so we list those revisions in full, below. - Log ----------------------------------------------------------------- https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=60f80624257ef84eacfd9b400bda1b5a5e8e7816 commit 60f80624257ef84eacfd9b400bda1b5a5e8e7816 Author: Florian Weimer <fweimer@redhat.com> Date: Fri Feb 8 12:55:21 2019 +0100 nptl: Avoid fork handler lock for async-signal-safe fork [BZ #24161] Commit 27761a1042daf01987e7d79636d0c41511c6df3c ("Refactor atfork handlers") introduced a lock, atfork_lock, around fork handler list accesses. It turns out that this lock occasionally results in self-deadlocks in malloc/tst-mallocfork2: (gdb) bt #0 __lll_lock_wait_private () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:63 #1 0x00007f160c6f927a in __run_fork_handlers (who=(unknown: 209394016), who@entry=atfork_run_prepare) at register-atfork.c:116 #2 0x00007f160c6b7897 in __libc_fork () at ../sysdeps/nptl/fork.c:58 #3 0x00000000004027d6 in sigusr1_handler (signo=<optimized out>) at tst-mallocfork2.c:80 #4 sigusr1_handler (signo=<optimized out>) at tst-mallocfork2.c:64 #5 <signal handler called> #6 0x00007f160c6f92e4 in __run_fork_handlers (who=who@entry=atfork_run_parent) at register-atfork.c:136 #7 0x00007f160c6b79a2 in __libc_fork () at ../sysdeps/nptl/fork.c:152 #8 0x0000000000402567 in do_test () at tst-mallocfork2.c:156 #9 0x0000000000402dd2 in support_test_main (argc=1, argv=0x7ffc81ef1ab0, config=config@entry=0x7ffc81ef1970) at support_test_main.c:350 #10 0x0000000000402362 in main (argc=<optimized out>, argv=<optimized out>) at ../support/test-driver.c:168 If no locking happens in the single-threaded case (where fork is expected to be async-signal-safe), this deadlock is avoided. (pthread_atfork is not required to be async-signal-safe, so a fork call from a signal handler interrupting pthread_atfork is not a problem.) (cherry picked from commit 669ff911e2571f74a2668493e326ac9a505776bd) ----------------------------------------------------------------------- Summary of changes: ChangeLog | 10 ++++++++++ NEWS | 1 + nptl/register-atfork.c | 8 +++++--- sysdeps/nptl/fork.c | 6 +++--- sysdeps/nptl/fork.h | 8 +++++--- 5 files changed, 24 insertions(+), 9 deletions(-)
This is an automated email from the git hooks/post-receive script. It was generated because a ref change was pushed to the repository containing the project "GNU C Library master sources". The branch, release/2.29/master has been updated via c096b008d2671028c21ac8cf01f18a2083e73c44 (commit) from 44113a8ba24af23d7bbb174f9087a6b83a76289a (commit) Those revisions listed above that are new to this repository have not appeared on any other notification email; so we list those revisions in full, below. - Log ----------------------------------------------------------------- https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=c096b008d2671028c21ac8cf01f18a2083e73c44 commit c096b008d2671028c21ac8cf01f18a2083e73c44 Author: Florian Weimer <fweimer@redhat.com> Date: Fri Feb 8 12:54:41 2019 +0100 nptl: Avoid fork handler lock for async-signal-safe fork [BZ #24161] Commit 27761a1042daf01987e7d79636d0c41511c6df3c ("Refactor atfork handlers") introduced a lock, atfork_lock, around fork handler list accesses. It turns out that this lock occasionally results in self-deadlocks in malloc/tst-mallocfork2: (gdb) bt #0 __lll_lock_wait_private () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:63 #1 0x00007f160c6f927a in __run_fork_handlers (who=(unknown: 209394016), who@entry=atfork_run_prepare) at register-atfork.c:116 #2 0x00007f160c6b7897 in __libc_fork () at ../sysdeps/nptl/fork.c:58 #3 0x00000000004027d6 in sigusr1_handler (signo=<optimized out>) at tst-mallocfork2.c:80 #4 sigusr1_handler (signo=<optimized out>) at tst-mallocfork2.c:64 #5 <signal handler called> #6 0x00007f160c6f92e4 in __run_fork_handlers (who=who@entry=atfork_run_parent) at register-atfork.c:136 #7 0x00007f160c6b79a2 in __libc_fork () at ../sysdeps/nptl/fork.c:152 #8 0x0000000000402567 in do_test () at tst-mallocfork2.c:156 #9 0x0000000000402dd2 in support_test_main (argc=1, argv=0x7ffc81ef1ab0, config=config@entry=0x7ffc81ef1970) at support_test_main.c:350 #10 0x0000000000402362 in main (argc=<optimized out>, argv=<optimized out>) at ../support/test-driver.c:168 If no locking happens in the single-threaded case (where fork is expected to be async-signal-safe), this deadlock is avoided. (pthread_atfork is not required to be async-signal-safe, so a fork call from a signal handler interrupting pthread_atfork is not a problem.) (cherry picked from commit 669ff911e2571f74a2668493e326ac9a505776bd) ----------------------------------------------------------------------- Summary of changes: ChangeLog | 10 ++++++++++ NEWS | 1 + nptl/register-atfork.c | 8 +++++--- sysdeps/nptl/fork.c | 6 +++--- sysdeps/nptl/fork.h | 8 +++++--- 5 files changed, 24 insertions(+), 9 deletions(-)