From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Tejun Heo <tj@kernel.org>,
Mike Galbraith <efault@gmx.de>, Kenny Yu <kennyyu@fb.com>
Subject: [PATCH 4.10 26/27] cgroup/pids: remove spurious suspicious RCU usage warning
Date: Fri, 24 Mar 2017 18:58:44 +0100 [thread overview]
Message-ID: <20170324151227.558323550@linuxfoundation.org> (raw)
In-Reply-To: <20170324151225.973768798@linuxfoundation.org>
4.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tejun Heo <tj@kernel.org>
commit 1d18c2747f937f1b5ec65ce6bf4ccb9ca1aea9e8 upstream.
pids_can_fork() is special in that the css association is guaranteed
to be stable throughout the function and thus doesn't need RCU
protection around task_css access. When determining the css to charge
the pid, task_css_check() is used to override the RCU sanity check.
While adding a warning message on fork rejection from pids limit,
135b8b37bd91 ("cgroup: Add pids controller event when fork fails
because of pid limit") incorrectly added a task_css access which is
neither RCU protected or explicitly annotated. This triggers the
following suspicious RCU usage warning when RCU debugging is enabled.
cgroup: fork rejected by pids controller in
===============================
[ ERR: suspicious RCU usage. ]
4.10.0-work+ #1 Not tainted
-------------------------------
./include/linux/cgroup.h:435 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 0
1 lock held by bash/1748:
#0: (&cgroup_threadgroup_rwsem){+++++.}, at: [<ffffffff81052c96>] _do_fork+0xe6/0x6e0
stack backtrace:
CPU: 3 PID: 1748 Comm: bash Not tainted 4.10.0-work+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.fc25 04/01/2014
Call Trace:
dump_stack+0x68/0x93
lockdep_rcu_suspicious+0xd7/0x110
pids_can_fork+0x1c7/0x1d0
cgroup_can_fork+0x67/0xc0
copy_process.part.58+0x1709/0x1e90
_do_fork+0xe6/0x6e0
SyS_clone+0x19/0x20
do_syscall_64+0x5c/0x140
entry_SYSCALL64_slow_path+0x25/0x25
RIP: 0033:0x7f7853fab93a
RSP: 002b:00007ffc12d05c90 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f7853fab93a
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007ffc12d05cc0 R08: 0000000000000000 R09: 00007f78548db700
R10: 00007f78548db9d0 R11: 0000000000000246 R12: 00000000000006d4
R13: 0000000000000001 R14: 0000000000000000 R15: 000055e3ebe2c04d
/asdf
There's no reason to dereference task_css again here when the
associated css is already available. Fix it by replacing the
task_cgroup() call with css->cgroup.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Mike Galbraith <efault@gmx.de>
Fixes: 135b8b37bd91 ("cgroup: Add pids controller event when fork fails because of pid limit")
Cc: Kenny Yu <kennyyu@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/cgroup_pids.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/cgroup_pids.c
+++ b/kernel/cgroup_pids.c
@@ -229,7 +229,7 @@ static int pids_can_fork(struct task_str
/* Only log the first time events_limit is incremented. */
if (atomic64_inc_return(&pids->events_limit) == 1) {
pr_info("cgroup: fork rejected by pids controller in ");
- pr_cont_cgroup_path(task_cgroup(current, pids_cgrp_id));
+ pr_cont_cgroup_path(css->cgroup);
pr_cont("\n");
}
cgroup_file_notify(&pids->events_file);
next prev parent reply other threads:[~2017-03-24 18:23 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-24 17:58 [PATCH 4.10 00/27] 4.10.6-stable review Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 01/27] give up on gcc ilog2() constant optimizations Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 02/27] qla2xxx: Fix memory leak for abts processing Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 03/27] qla2xxx: Fix request queue corruption Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 04/27] parisc: Optimize flush_kernel_vmap_range and invalidate_kernel_vmap_range Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 05/27] parisc: support R_PARISC_SECREL32 relocation in modules Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 06/27] parisc: Fix system shutdown halt Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 07/27] perf/core: Fix use-after-free in perf_release() Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 08/27] perf/core: Fix event inheritance on fork() Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 09/27] md/r5cache: fix set_syndrome_sources() for data in cache Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 10/27] xprtrdma: Squelch kbuild sparse complaint Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 11/27] NFS prevent double free in async nfs4_exchange_id Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 12/27] cpufreq: Fix and clean up show_cpuinfo_cur_freq() Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 13/27] powerpc/boot: Fix zImage TOC alignment Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 14/27] hwrng: omap - write registers after enabling the clock Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 15/27] hwrng: omap - use devm_clk_get() instead of of_clk_get() Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 16/27] hwrng: omap - Do not access INTMASK_REG on EIP76 Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 17/27] md/raid1/10: fix potential deadlock Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 18/27] target/pscsi: Fix TYPE_TAPE + TYPE_MEDIMUM_CHANGER export Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 19/27] scsi: lpfc: Add shutdown method for kexec Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 20/27] scsi: libiscsi: add lock around task lists to fix list corruption regression Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 21/27] scsi: mpt3sas: Avoid sleeping in interrupt context Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 22/27] target: Fix VERIFY_16 handling in sbc_parse_cdb Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 23/27] isdn/gigaset: fix NULL-deref at probe Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 24/27] gfs2: Avoid alignment hole in struct lm_lockname Greg Kroah-Hartman
2017-03-24 17:58 ` [PATCH 4.10 25/27] percpu: acquire pcpu_lock when updating pcpu_nr_empty_pop_pages Greg Kroah-Hartman
2017-03-24 17:58 ` Greg Kroah-Hartman [this message]
2017-03-25 0:00 ` [PATCH 4.10 00/27] 4.10.6-stable review Shuah Khan
2017-03-26 8:19 ` Greg Kroah-Hartman
2017-03-25 4:18 ` Guenter Roeck
2017-03-26 8:51 ` Greg Kroah-Hartman
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