From: Andrew Morton <akpm@linux-foundation.org>
To: tj@kernel.org,tglx@linutronix.de,lizefan.x@bytedance.com,hannes@cmpxchg.org,bigeasy@linutronix.de,akpm@linux-foundation.org,patches@lists.linux.dev,linux-mm@kvack.org,mm-commits@vger.kernel.org,torvalds@linux-foundation.org,akpm@linux-foundation.org
Subject: [patch 24/41] cgroup: use irqsave in cgroup_rstat_flush_locked().
Date: Wed, 23 Mar 2022 16:06:29 -0700 [thread overview]
Message-ID: <20220323230630.8C004C340E8@smtp.kernel.org> (raw)
In-Reply-To: <20220323160453.65922ced539cbf445b191555@linux-foundation.org>
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: cgroup: use irqsave in cgroup_rstat_flush_locked().
All callers of cgroup_rstat_flush_locked() acquire cgroup_rstat_lock
either with spin_lock_irq() or spin_lock_irqsave().
cgroup_rstat_flush_locked() itself acquires cgroup_rstat_cpu_lock which is
a raw_spin_lock. This lock is also acquired in cgroup_rstat_updated() in
IRQ context and therefore requires _irqsave() locking suffix in
cgroup_rstat_flush_locked().
Since there is no difference between spin_lock_t and raw_spin_lock_t on
!RT lockdep does not complain here. On RT lockdep complains because the
interrupts were not disabled here and a deadlock is possible.
Acquire the raw_spin_lock_t with disabled interrupts.
Link: https://lkml.kernel.org/r/20220301122143.1521823-2-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Zefan Li <lizefan.x@bytedance.com>
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: cgroup: add a comment to cgroup_rstat_flush_locked().
Add a comment why spin_lock_irq() -> raw_spin_lock_irqsave() is needed.
Link: https://lkml.kernel.org/r/Yh+DOK73hfVV5ThX@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
kernel/cgroup/rstat.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
--- a/kernel/cgroup/rstat.c~cgroup-use-irqsave-in-cgroup_rstat_flush_locked
+++ a/kernel/cgroup/rstat.c
@@ -153,8 +153,17 @@ static void cgroup_rstat_flush_locked(st
raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock,
cpu);
struct cgroup *pos = NULL;
+ unsigned long flags;
- raw_spin_lock(cpu_lock);
+ /*
+ * The _irqsave() is needed because cgroup_rstat_lock is
+ * spinlock_t which is a sleeping lock on PREEMPT_RT. Acquiring
+ * this lock with the _irq() suffix only disables interrupts on
+ * a non-PREEMPT_RT kernel. The raw_spinlock_t below disables
+ * interrupts on both configurations. The _irqsave() ensures
+ * that interrupts are always disabled and later restored.
+ */
+ raw_spin_lock_irqsave(cpu_lock, flags);
while ((pos = cgroup_rstat_cpu_pop_updated(pos, cgrp, cpu))) {
struct cgroup_subsys_state *css;
@@ -166,7 +175,7 @@ static void cgroup_rstat_flush_locked(st
css->ss->css_rstat_flush(css, cpu);
rcu_read_unlock();
}
- raw_spin_unlock(cpu_lock);
+ raw_spin_unlock_irqrestore(cpu_lock, flags);
/* if @may_sleep, play nice and yield if necessary */
if (may_sleep && (need_resched() ||
_
next prev parent reply other threads:[~2022-03-23 23:06 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-23 23:04 incoming Andrew Morton
2022-03-23 23:05 ` [patch 01/41] proc: alloc PATH_MAX bytes for /proc/${pid}/fd/ symlinks Andrew Morton
2022-03-23 23:05 ` [patch 02/41] proc/vmcore: fix possible deadlock on concurrent mmap and read Andrew Morton
2022-03-23 23:05 ` [patch 03/41] proc/vmcore: fix vmcore_alloc_buf() kernel-doc comment Andrew Morton
2022-03-23 23:05 ` [patch 04/41] linux/types.h: remove unnecessary __bitwise__ Andrew Morton
2022-03-23 23:05 ` [patch 05/41] Documentation/sparse: add hints about __CHECKER__ Andrew Morton
2022-03-23 23:05 ` [patch 06/41] kernel/ksysfs.c: use helper macro __ATTR_RW Andrew Morton
2022-03-23 23:05 ` [patch 07/41] Kconfig.debug: make DEBUG_INFO selectable from a choice Andrew Morton
2022-03-23 23:05 ` [patch 08/41] include: drop pointless __compiler_offsetof indirection Andrew Morton
2022-03-23 23:05 ` [patch 09/41] ilog2: force inlining of __ilog2_u32() and __ilog2_u64() Andrew Morton
2022-03-23 23:05 ` [patch 10/41] bitfield: add explicit inclusions to the example Andrew Morton
2022-03-23 23:05 ` [patch 11/41] lib/Kconfig.debug: add ARCH dependency for FUNCTION_ALIGN option Andrew Morton
2022-03-23 23:05 ` [patch 12/41] lib: bitmap: fix many kernel-doc warnings Andrew Morton
2022-03-23 23:05 ` [patch 13/41] checkpatch: prefer MODULE_LICENSE("GPL") over MODULE_LICENSE("GPL v2") Andrew Morton
2022-03-23 23:05 ` [patch 14/41] checkpatch: add --fix option for some TRAILING_STATEMENTS Andrew Morton
2022-03-23 23:06 ` [patch 15/41] checkpatch: add early_param exception to blank line after struct/function test Andrew Morton
2022-03-23 23:06 ` [patch 16/41] checkpatch: use python3 to find codespell dictionary Andrew Morton
2022-03-23 23:06 ` [patch 17/41] init: use ktime_us_delta() to make initcall_debug log more precise Andrew Morton
2022-03-23 23:06 ` [patch 18/41] init.h: improve __setup and early_param documentation Andrew Morton
2022-03-23 23:06 ` [patch 19/41] init/main.c: return 1 from handled __setup() functions Andrew Morton
2022-03-23 23:06 ` [patch 20/41] fs/pipe: use kvcalloc to allocate a pipe_buffer array Andrew Morton
2022-03-23 23:06 ` [patch 21/41] fs/pipe.c: local vars have to match types of proper pipe_inode_info fields Andrew Morton
2022-03-23 23:06 ` [patch 22/41] minix: fix bug when opening a file with O_DIRECT Andrew Morton
2022-03-23 23:06 ` [patch 23/41] fat: use pointer to simple type in put_user() Andrew Morton
2022-03-23 23:06 ` Andrew Morton [this message]
2022-03-23 23:06 ` [patch 25/41] kexec: make crashk_res, crashk_low_res and crash_notes symbols always visible Andrew Morton
2022-03-23 23:06 ` [patch 26/41] riscv: mm: init: use IS_ENABLED(CONFIG_KEXEC_CORE) instead of #ifdef Andrew Morton
2022-03-23 23:06 ` [patch 27/41] x86/setup: " Andrew Morton
2022-03-23 23:06 ` [patch 28/41] arm64: mm: " Andrew Morton
2022-03-23 23:06 ` [patch 29/41] docs: kdump: update description about sysfs file system support Andrew Morton
2022-03-23 23:06 ` [patch 30/41] docs: kdump: add scp example to write out the dump file Andrew Morton
2022-03-23 23:06 ` [patch 31/41] panic: unset panic_on_warn inside panic() Andrew Morton
2022-03-23 23:06 ` [patch 32/41] ubsan: no need to unset panic_on_warn in ubsan_epilogue() Andrew Morton
2022-03-23 23:06 ` [patch 33/41] kasan: no need to unset panic_on_warn in end_report() Andrew Morton
2022-03-23 23:07 ` [patch 34/41] taskstats: remove unneeded dead assignment Andrew Morton
2022-03-23 23:07 ` [patch 35/41] docs: sysctl/kernel: add missing bit to panic_print Andrew Morton
2022-03-23 23:07 ` [patch 36/41] panic: add option to dump all CPUs backtraces in panic_print Andrew Morton
2022-03-23 23:07 ` [patch 37/41] panic: move panic_print before kmsg dumpers Andrew Morton
2022-03-23 23:07 ` [patch 38/41] kcov: split ioctl handling into locked and unlocked parts Andrew Morton
2022-03-23 23:07 ` [patch 39/41] kcov: properly handle subsequent mmap calls Andrew Morton
2022-03-23 23:07 ` [patch 40/41] kernel/resource: fix kfree() of bootmem memory again Andrew Morton
2022-03-23 23:07 ` [patch 41/41] Revert "ubsan, kcsan: Don't combine sanitizer with kcov on clang" Andrew Morton
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