https://github.com/torvalds/linux
Revision 735f2770a770156100f534646158cb58cb8b2939 authored by Michal Hocko on 01 September 2016, 23:15:13 UTC, committed by Linus Torvalds on 02 September 2016, 00:52:02 UTC
Commit fec1d0115240 ("[PATCH] Disable CLONE_CHILD_CLEARTID for abnormal exit") has caused a subtle regression in nscd which uses CLONE_CHILD_CLEARTID to clear the nscd_certainly_running flag in the shared databases, so that the clients are notified when nscd is restarted. Now, when nscd uses a non-persistent database, clients that have it mapped keep thinking the database is being updated by nscd, when in fact nscd has created a new (anonymous) one (for non-persistent databases it uses an unlinked file as backend). The original proposal for the CLONE_CHILD_CLEARTID change claimed (https://lkml.org/lkml/2006/10/25/233): : The NPTL library uses the CLONE_CHILD_CLEARTID flag on clone() syscalls : on behalf of pthread_create() library calls. This feature is used to : request that the kernel clear the thread-id in user space (at an address : provided in the syscall) when the thread disassociates itself from the : address space, which is done in mm_release(). : : Unfortunately, when a multi-threaded process incurs a core dump (such as : from a SIGSEGV), the core-dumping thread sends SIGKILL signals to all of : the other threads, which then proceed to clear their user-space tids : before synchronizing in exit_mm() with the start of core dumping. This : misrepresents the state of process's address space at the time of the : SIGSEGV and makes it more difficult for someone to debug NPTL and glibc : problems (misleading him/her to conclude that the threads had gone away : before the fault). : : The fix below is to simply avoid the CLONE_CHILD_CLEARTID action if a : core dump has been initiated. The resulting patch from Roland (https://lkml.org/lkml/2006/10/26/269) seems to have a larger scope than the original patch asked for. It seems that limitting the scope of the check to core dumping should work for SIGSEGV issue describe above. [Changelog partly based on Andreas' description] Fixes: fec1d0115240 ("[PATCH] Disable CLONE_CHILD_CLEARTID for abnormal exit") Link: http://lkml.kernel.org/r/1471968749-26173-1-git-send-email-mhocko@kernel.org Signed-off-by: Michal Hocko <mhocko@suse.com> Tested-by: William Preston <wpreston@suse.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@hack.frob.com> Cc: Andreas Schwab <schwab@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent c4e2973
Tip revision: 735f2770a770156100f534646158cb58cb8b2939 authored by Michal Hocko on 01 September 2016, 23:15:13 UTC
kernel/fork: fix CLONE_CHILD_CLEARTID regression in nscd
kernel/fork: fix CLONE_CHILD_CLEARTID regression in nscd
Tip revision: 735f277
File | Mode | Size |
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Kconfig | -rw-r--r-- | 3.7 KB |
Kconfig.iosched | -rw-r--r-- | 1.6 KB |
Makefile | -rw-r--r-- | 922 bytes |
badblocks.c | -rw-r--r-- | 14.1 KB |
bio-integrity.c | -rw-r--r-- | 14.2 KB |
bio.c | -rw-r--r-- | 48.5 KB |
blk-cgroup.c | -rw-r--r-- | 35.8 KB |
blk-core.c | -rw-r--r-- | 93.1 KB |
blk-exec.c | -rw-r--r-- | 3.2 KB |
blk-flush.c | -rw-r--r-- | 15.4 KB |
blk-integrity.c | -rw-r--r-- | 12.3 KB |
blk-ioc.c | -rw-r--r-- | 10.2 KB |
blk-lib.c | -rw-r--r-- | 6.9 KB |
blk-map.c | -rw-r--r-- | 5.8 KB |
blk-merge.c | -rw-r--r-- | 19.6 KB |
blk-mq-cpu.c | -rw-r--r-- | 1.6 KB |
blk-mq-cpumap.c | -rw-r--r-- | 2.6 KB |
blk-mq-sysfs.c | -rw-r--r-- | 11.4 KB |
blk-mq-tag.c | -rw-r--r-- | 17.4 KB |
blk-mq-tag.h | -rw-r--r-- | 2.6 KB |
blk-mq.c | -rw-r--r-- | 58.0 KB |
blk-mq.h | -rw-r--r-- | 3.3 KB |
blk-settings.c | -rw-r--r-- | 27.0 KB |
blk-softirq.c | -rw-r--r-- | 4.4 KB |
blk-sysfs.c | -rw-r--r-- | 18.5 KB |
blk-tag.c | -rw-r--r-- | 10.0 KB |
blk-throttle.c | -rw-r--r-- | 42.5 KB |
blk-timeout.c | -rw-r--r-- | 5.9 KB |
blk.h | -rw-r--r-- | 9.1 KB |
bounce.c | -rw-r--r-- | 5.8 KB |
bsg-lib.c | -rw-r--r-- | 6.0 KB |
bsg.c | -rw-r--r-- | 22.9 KB |
cfq-iosched.c | -rw-r--r-- | 127.0 KB |
cmdline-parser.c | -rw-r--r-- | 4.9 KB |
compat_ioctl.c | -rw-r--r-- | 20.8 KB |
deadline-iosched.c | -rw-r--r-- | 11.3 KB |
elevator.c | -rw-r--r-- | 23.8 KB |
genhd.c | -rw-r--r-- | 45.0 KB |
ioctl.c | -rw-r--r-- | 14.6 KB |
ioprio.c | -rw-r--r-- | 5.1 KB |
noop-iosched.c | -rw-r--r-- | 2.6 KB |
partition-generic.c | -rw-r--r-- | 14.7 KB |
scsi_ioctl.c | -rw-r--r-- | 19.4 KB |
t10-pi.c | -rw-r--r-- | 4.8 KB |
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