ab6c41eefd
From time to time there are lockdep reports similar to this one:
WARNING: possible circular locking dependency detected
------------------------------------------------------
000000004f61aa56 (&table[i].mutex){+.+.}, at: nfnl_lock [nfnetlink]
but task is already holding lock:
[..] (&net->nft.commit_mutex){+.+.}, at: nf_tables_valid_genid [nf_tables]
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&net->nft.commit_mutex){+.+.}:
[..]
nf_tables_valid_genid+0x18/0x60 [nf_tables]
nfnetlink_rcv_batch+0x24c/0x620 [nfnetlink]
nfnetlink_rcv+0x110/0x140 [nfnetlink]
netlink_unicast+0x12c/0x1e0
[..]
sys_sendmsg+0x18/0x40
linux_sparc_syscall+0x34/0x44
-> #0 (&table[i].mutex){+.+.}:
[..]
nfnl_lock+0x24/0x40 [nfnetlink]
ip_set_nfnl_get_byindex+0x19c/0x280 [ip_set]
set_match_v1_checkentry+0x14/0xc0 [xt_set]
xt_check_match+0x238/0x260 [x_tables]
__nft_match_init+0x160/0x180 [nft_compat]
[..]
sys_sendmsg+0x18/0x40
linux_sparc_syscall+0x34/0x44
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&net->nft.commit_mutex);
lock(&table[i].mutex);
lock(&net->nft.commit_mutex);
lock(&table[i].mutex);
Lockdep considers this an ABBA deadlock because the different nfnl subsys
mutexes reside in the same lockdep class, but this is a false positive.
CPU1 table[i] refers to the nftables subsys mutex, whereas CPU1 locks
the ipset subsys mutex.
Yi Che reported a similar lockdep splat, this time between ipset and
ctnetlink subsys mutexes.
Time to place them in distinct classes to avoid these warnings.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.