Date: Mon, 4 Jan 2016 22:05:21 -0800 From: Benno Rice <benno@FreeBSD.org> To: Konstantin Belousov <kib@freebsd.org> Cc: freebsd-current <freebsd-current@freebsd.org> Subject: Possible bug in or around posix_fadvise after r292326 Message-ID: <ACCB7B60-A8BA-418D-BE71-EC4E83693FFA@FreeBSD.org>
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Hi Konstantin,
I recently updated my dev box to r292962. After doing this I attempted =
to set up PostgreSQL 9.4. When I ran initdb the last phase hung. Using =
procstat -kk I found it appeared to be stuck in a loop inside a =
posix_fadvise syscall. I could not ^C or ^Z the initdb process. I could =
kill it but a subsequent attempt to rm -rf the /usr/local/pgsql/data =
directory also got stuck and was unkillable by any means. Rebooting =
allowed me to remove the directory but the initdb process still hung =
when I re-ran it.
I tried PostgreSQL 9.3 with similar results.
Looking at the source code for initdb I found that it calls =
posix_fadvise like so[1]:
/*
* We do what pg_flush_data() would do in the backend: prefer to =
use
* sync_file_range, but fall back to posix_fadvise. We ignore =
errors
* because this is only a hint.
*/
#if defined(HAVE_SYNC_FILE_RANGE)
(void) sync_file_range(fd, 0, 0, SYNC_FILE_RANGE_WRITE);
#elif defined(USE_POSIX_FADVISE) && defined(POSIX_FADV_DONTNEED)
(void) posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED);
#else
#error PG_FLUSH_DATA_WORKS should not have been defined
#endif
Looking for recent commits involving POSIX_FADV_DONTNEED I found =
r292326:
https://svnweb.freebsd.org/changeset/base/292326 =
<https://svnweb.freebsd.org/changeset/base/292326>;
Backing this revision out allowed the initdb process to complete.
My current theory is that some how we=E2=80=99re getting ENOLCK or =
EAGAIN from the BUF_TIMELOCK call in bnoreuselist:
=
https://svnweb.freebsd.org/base/head/sys/kern/vfs_subr.c?view=3Dannotate#l=
1676 =
<https://svnweb.freebsd.org/base/head/sys/kern/vfs_subr.c?view=3Dannotate#=
l1676>
Leading to an infinite loop in vop_stdadvise:
=
https://svnweb.freebsd.org/base/head/sys/kern/vfs_default.c?annotate=3D292=
373#l1083 =
<https://svnweb.freebsd.org/base/head/sys/kern/vfs_default.c?annotate=3D29=
2373#l1083>
I haven=E2=80=99t managed to dig any deeper than that yet.
Is there any other information I could give you to help narrow this =
down?
Thanks,
Benno.
[1] =
http://git.postgresql.org/gitweb/?p=3Dpostgresql.git;a=3Dblob;f=3Dsrc/bin/=
initdb/initdb.c;h=3D35e39ce4b31b2f437d6e28eaf90500a22d229c6a;hb=3DHEAD#l63=
1=
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