SGI has observed that on large systems, interrupts are not serviced for a
long period of time when waiting for a rwlock. The following patch series
re-enables irqs while waiting for the lock, resembling the code which is
already there for spinlocks.
I only made the ia64 version, because the patch adds some overhead to the
fast path. I assume there is currently no demand to have this for other
architectures, because the systems are not so large. Of course, the
possibility to implement raw_{read|write}_lock_flags for any architecture
is still there.
This patch:
The new macro LOCK_CONTENDED_FLAGS expands to the correct implementation
depending on the config options, so that IRQ's are re-enabled when
possible, but they remain disabled if CONFIG_LOCKDEP is set.
Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
Signed-off-by: Robin Holt <holt@sgi.com>
Cc: <linux-arch@vger.kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
For convenience later. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
s/HELD_OVER/ENABLED/g so that its similar to the hard and soft-irq names. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
s/\(LOCKF\?_ENABLED_[^ ]*\)S\(_READ\)\?\>/\1\2/g So that the USED_IN and ENABLED have the same names. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Here is another version, with the incremental patch rolled up, and
added reclaim context annotation to kswapd, and allocation tracing
to slab allocators (which may only ever reach the page allocator
in rare cases, so it is good to put annotations here too).
Haven't tested this version as such, but it should be getting closer
to merge worthy ;)
--
After noticing some code in mm/filemap.c accidentally perform a __GFP_FS
allocation when it should not have been, I thought it might be a good idea to
try to catch this kind of thing with lockdep.
I coded up a little idea that seems to work. Unfortunately the system has to
actually be in __GFP_FS page reclaim, then take the lock, before it will mark
it. But at least that might still be some orders of magnitude more common
(and more debuggable) than an actual deadlock condition, so we have some
improvement I hope (the concept is no less complete than discovery of a lock's
interrupt contexts).
I guess we could even do the same thing with __GFP_IO (normal reclaim), and
even GFP_NOIO locks too... but filesystems will have the most locks and fiddly
code paths, so let's start there and see how it goes.
It *seems* to work. I did a quick test.
=================================
[ INFO: inconsistent lock state ]
2.6.28-rc6-00007-ged31348-dirty #26
---------------------------------
inconsistent {in-reclaim-W} -> {ov-reclaim-W} usage.
modprobe/8526 [HC0[0]:SC0[0]:HE1:SE1] takes:
(testlock){--..}, at: [<ffffffffa0020055>] brd_init+0x55/0x216 [brd]
{in-reclaim-W} state was registered at:
[<ffffffff80267bdb>] __lock_acquire+0x75b/0x1a60
[<ffffffff80268f71>] lock_acquire+0x91/0xc0
[<ffffffff8070f0e1>] mutex_lock_nested+0xb1/0x310
[<ffffffffa002002b>] brd_init+0x2b/0x216 [brd]
[<ffffffff8020903b>] _stext+0x3b/0x170
[<ffffffff80272ebf>] sys_init_module+0xaf/0x1e0
[<ffffffff8020c3fb>] system_call_fastpath+0x16/0x1b
[<ffffffffffffffff>] 0xffffffffffffffff
irq event stamp: 3929
hardirqs last enabled at (3929): [<ffffffff8070f2b5>] mutex_lock_nested+0x285/0x310
hardirqs last disabled at (3928): [<ffffffff8070f089>] mutex_lock_nested+0x59/0x310
softirqs last enabled at (3732): [<ffffffff8061f623>] sk_filter+0x83/0xe0
softirqs last disabled at (3730): [<ffffffff8061f5b6>] sk_filter+0x16/0xe0
other info that might help us debug this:
1 lock held by modprobe/8526:
#0: (testlock){--..}, at: [<ffffffffa0020055>] brd_init+0x55/0x216 [brd]
stack backtrace:
Pid: 8526, comm: modprobe Not tainted 2.6.28-rc6-00007-ged31348-dirty #26
Call Trace:
[<ffffffff80265483>] print_usage_bug+0x193/0x1d0
[<ffffffff80266530>] mark_lock+0xaf0/0xca0
[<ffffffff80266735>] mark_held_locks+0x55/0xc0
[<ffffffffa0020000>] ? brd_init+0x0/0x216 [brd]
[<ffffffff802667ca>] trace_reclaim_fs+0x2a/0x60
[<ffffffff80285005>] __alloc_pages_internal+0x475/0x580
[<ffffffff8070f29e>] ? mutex_lock_nested+0x26e/0x310
[<ffffffffa0020000>] ? brd_init+0x0/0x216 [brd]
[<ffffffffa002006a>] brd_init+0x6a/0x216 [brd]
[<ffffffffa0020000>] ? brd_init+0x0/0x216 [brd]
[<ffffffff8020903b>] _stext+0x3b/0x170
[<ffffffff8070f8b9>] ? mutex_unlock+0x9/0x10
[<ffffffff8070f83d>] ? __mutex_unlock_slowpath+0x10d/0x180
[<ffffffff802669ec>] ? trace_hardirqs_on_caller+0x12c/0x190
[<ffffffff80272ebf>] sys_init_module+0xaf/0x1e0
[<ffffffff8020c3fb>] system_call_fastpath+0x16/0x1b
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: x86, sparseirq: clean up Kconfig entry x86: turn CONFIG_SPARSE_IRQ off by default sparseirq: fix numa_migrate_irq_desc dependency and comments sparseirq: add kernel-doc notation for new member in irq_desc, -v2 locking, irq: enclose irq_desc_lock_class in CONFIG_LOCKDEP sparseirq, xen: make sure irq_desc is allocated for interrupts sparseirq: fix !SMP building, #2 x86, sparseirq: move irq_desc according to smp_affinity, v7 proc: enclose desc variable of show_stat() in CONFIG_SPARSE_IRQ sparse irqs: add irqnr.h to the user headers list sparse irqs: handle !GENIRQ platforms sparseirq: fix !SMP && !PCI_MSI && !HT_IRQ build sparseirq: fix Alpha build failure sparseirq: fix typo in !CONFIG_IO_APIC case x86, MSI: pass irq_cfg and irq_desc x86: MSI start irq numbering from nr_irqs_gsi x86: use NR_IRQS_LEGACY sparse irq_desc[] array: core kernel and x86 changes genirq: record IRQ_LEVEL in irq_desc[] irq.h: remove padding from irq_desc on 64bits
Impact: simplify code commit "08678b0: generic: sparse irqs: use irq_desc() [...]" introduced the irq_desc_lock_class variable. But it is used only if CONFIG_SPARSE_IRQ=Y or CONFIG_TRACE_IRQFLAGS=Y. Otherwise, following warnings happen: CC kernel/irq/handle.o kernel/irq/handle.c:26: warning: 'irq_desc_lock_class' defined but not used Actually, current early_init_irq_lock_class has a bit strange and messy ifdef. In addition, it is not valueable. 1. this function is protected by !CONFIG_SPARSE_IRQ, but that is not necessary. if CONFIG_SPARSE_IRQ=Y, desc of all irq number are initialized by NULL at first - then this function calling is safe. 2. this function protected by CONFIG_TRACE_IRQFLAGS too. but it is not necessary either, because lockdep_set_class() doesn't have bad side effect even if CONFIG_TRACE_IRQFLAGS=n. This patch bloat kernel size a bit on CONFIG_TRACE_IRQFLAGS=n and CONFIG_SPARSE_IRQ=Y - but that's ok. early_init_irq_lock_class() is not a fastpatch at all. To avoid messy ifdefs is more important than a few bytes diet. Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: introduce new lockdep API Allow to change a held lock's class. Basically the same as the existing code to change a subclass therefore reuse all that. The XFS code will be able to use this to annotate their inode locking. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
fix this warning: net/bluetooth/af_bluetooth.c:60: warning: ‘bt_key_strings’ defined but not used net/bluetooth/af_bluetooth.c:71: warning: ‘bt_slock_key_strings’ defined but not used this is a lockdep macro problem in the !LOCKDEP case. We cannot convert it to an inline because the macro works on multiple types, but we can mark the parameter used. [ also clean up a misaligned tab in sock_lock_init_class_and_name() ] [ also remove #ifdefs from around af_family_clock_key strings - which were certainly added to get rid of the ugly build warnings. ] Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: David S. Miller <davem@davemloft.net>
fix this warning: net/bluetooth/af_bluetooth.c:60: warning: ‘bt_key_strings’ defined but not used net/bluetooth/af_bluetooth.c:71: warning: ‘bt_slock_key_strings’ defined but not used this is a lockdep macro problem in the !LOCKDEP case. We cannot convert it to an inline because the macro works on multiple types, but we can mark the parameter used. [ also clean up a misaligned tab in sock_lock_init_class_and_name() ] [ also remove #ifdefs from around af_family_clock_key strings - which were certainly added to get rid of the ugly build warnings. ] Signed-off-by: Ingo Molnar <mingo@elte.hu>