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405 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
 Peter Zijlstra
|
04dc1b2fff |
futex,rt_mutex: Fix rt_mutex_cleanup_proxy_lock()
Markus reported that the glibc/nptl/tst-robustpi8 test was failing after commit: |
||
 Linus Torvalds
|
de4d195308 |
Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU updates from Ingo Molnar: "The main changes are: - Debloat RCU headers - Parallelize SRCU callback handling (plus overlapping patches) - Improve the performance of Tree SRCU on a CPU-hotplug stress test - Documentation updates - Miscellaneous fixes" * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (74 commits) rcu: Open-code the rcu_cblist_n_lazy_cbs() function rcu: Open-code the rcu_cblist_n_cbs() function rcu: Open-code the rcu_cblist_empty() function rcu: Separately compile large rcu_segcblist functions srcu: Debloat the <linux/rcu_segcblist.h> header srcu: Adjust default auto-expediting holdoff srcu: Specify auto-expedite holdoff time srcu: Expedite first synchronize_srcu() when idle srcu: Expedited grace periods with reduced memory contention srcu: Make rcutorture writer stalls print SRCU GP state srcu: Exact tracking of srcu_data structures containing callbacks srcu: Make SRCU be built by default srcu: Fix Kconfig botch when SRCU not selected rcu: Make non-preemptive schedule be Tasks RCU quiescent state srcu: Expedite srcu_schedule_cbs_snp() callback invocation srcu: Parallelize callback handling kvm: Move srcu_struct fields to end of struct kvm rcu: Fix typo in PER_RCU_NODE_PERIOD header comment rcu: Use true/false in assignment to bool rcu: Use bool value directly ... |
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Linus Torvalds
|
dd23f273d9 |
Merge branch 'akpm' (patches from Andrew)
Merge misc updates from Andrew Morton: - a few misc things - most of MM - KASAN updates * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (102 commits) kasan: separate report parts by empty lines kasan: improve double-free report format kasan: print page description after stacks kasan: improve slab object description kasan: change report header kasan: simplify address description logic kasan: change allocation and freeing stack traces headers kasan: unify report headers kasan: introduce helper functions for determining bug type mm: hwpoison: call shake_page() after try_to_unmap() for mlocked page mm: hwpoison: call shake_page() unconditionally mm/swapfile.c: fix swap space leak in error path of swap_free_entries() mm/gup.c: fix access_ok() argument type mm/truncate: avoid pointless cleancache_invalidate_inode() calls. mm/truncate: bail out early from invalidate_inode_pages2_range() if mapping is empty fs/block_dev: always invalidate cleancache in invalidate_bdev() fs: fix data invalidation in the cleancache during direct IO zram: reduce load operation in page_same_filled zram: use zram_free_page instead of open-coded zram: introduce zram data accessor ... |
||
 Michal Hocko
|
7dea19f9ee |
mm: introduce memalloc_nofs_{save,restore} API
GFP_NOFS context is used for the following 5 reasons currently:
- to prevent from deadlocks when the lock held by the allocation
context would be needed during the memory reclaim
- to prevent from stack overflows during the reclaim because the
allocation is performed from a deep context already
- to prevent lockups when the allocation context depends on other
reclaimers to make a forward progress indirectly
- just in case because this would be safe from the fs POV
- silence lockdep false positives
Unfortunately overuse of this allocation context brings some problems to
the MM. Memory reclaim is much weaker (especially during heavy FS
metadata workloads), OOM killer cannot be invoked because the MM layer
doesn't have enough information about how much memory is freeable by the
FS layer.
In many cases it is far from clear why the weaker context is even used
and so it might be used unnecessarily. We would like to get rid of
those as much as possible. One way to do that is to use the flag in
scopes rather than isolated cases. Such a scope is declared when really
necessary, tracked per task and all the allocation requests from within
the context will simply inherit the GFP_NOFS semantic.
Not only this is easier to understand and maintain because there are
much less problematic contexts than specific allocation requests, this
also helps code paths where FS layer interacts with other layers (e.g.
crypto, security modules, MM etc...) and there is no easy way to convey
the allocation context between the layers.
Introduce memalloc_nofs_{save,restore} API to control the scope of
GFP_NOFS allocation context. This is basically copying
memalloc_noio_{save,restore} API we have for other restricted allocation
context GFP_NOIO. The PF_MEMALLOC_NOFS flag already exists and it is
just an alias for PF_FSTRANS which has been xfs specific until recently.
There are no more PF_FSTRANS users anymore so let's just drop it.
PF_MEMALLOC_NOFS is now checked in the MM layer and drops __GFP_FS
implicitly same as PF_MEMALLOC_NOIO drops __GFP_IO. memalloc_noio_flags
is renamed to current_gfp_context because it now cares about both
PF_MEMALLOC_NOFS and PF_MEMALLOC_NOIO contexts. Xfs code paths preserve
their semantic. kmem_flags_convert() doesn't need to evaluate the flag
anymore.
This patch shouldn't introduce any functional changes.
Let's hope that filesystems will drop direct GFP_NOFS (resp. ~__GFP_FS)
usage as much as possible and only use a properly documented
memalloc_nofs_{save,restore} checkpoints where they are appropriate.
[akpm@linux-foundation.org: fix comment typo, reflow comment]
Link: http://lkml.kernel.org/r/20170306131408.9828-5-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Chris Mason <clm@fb.com>
Cc: David Sterba <dsterba@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Brian Foster <bfoster@redhat.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Nikolay Borisov <nborisov@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
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Michal Hocko
|
7e7844226f |
lockdep: allow to disable reclaim lockup detection
The current implementation of the reclaim lockup detection can lead to false positives and those even happen and usually lead to tweak the code to silence the lockdep by using GFP_NOFS even though the context can use __GFP_FS just fine. See http://lkml.kernel.org/r/20160512080321.GA18496@dastard as an example. ================================= [ INFO: inconsistent lock state ] 4.5.0-rc2+ #4 Tainted: G O --------------------------------- inconsistent {RECLAIM_FS-ON-R} -> {IN-RECLAIM_FS-W} usage. kswapd0/543 [HC0[0]:SC0[0]:HE1:SE1] takes: (&xfs_nondir_ilock_class){++++-+}, at: xfs_ilock+0x177/0x200 [xfs] {RECLAIM_FS-ON-R} state was registered at: mark_held_locks+0x79/0xa0 lockdep_trace_alloc+0xb3/0x100 kmem_cache_alloc+0x33/0x230 kmem_zone_alloc+0x81/0x120 [xfs] xfs_refcountbt_init_cursor+0x3e/0xa0 [xfs] __xfs_refcount_find_shared+0x75/0x580 [xfs] xfs_refcount_find_shared+0x84/0xb0 [xfs] xfs_getbmap+0x608/0x8c0 [xfs] xfs_vn_fiemap+0xab/0xc0 [xfs] do_vfs_ioctl+0x498/0x670 SyS_ioctl+0x79/0x90 entry_SYSCALL_64_fastpath+0x12/0x6f CPU0 ---- lock(&xfs_nondir_ilock_class); <Interrupt> lock(&xfs_nondir_ilock_class); *** DEADLOCK *** 3 locks held by kswapd0/543: stack backtrace: CPU: 0 PID: 543 Comm: kswapd0 Tainted: G O 4.5.0-rc2+ #4 Call Trace: lock_acquire+0xd8/0x1e0 down_write_nested+0x5e/0xc0 xfs_ilock+0x177/0x200 [xfs] xfs_reflink_cancel_cow_range+0x150/0x300 [xfs] xfs_fs_evict_inode+0xdc/0x1e0 [xfs] evict+0xc5/0x190 dispose_list+0x39/0x60 prune_icache_sb+0x4b/0x60 super_cache_scan+0x14f/0x1a0 shrink_slab.part.63.constprop.79+0x1e9/0x4e0 shrink_zone+0x15e/0x170 kswapd+0x4f1/0xa80 kthread+0xf2/0x110 ret_from_fork+0x3f/0x70 To quote Dave: "Ignoring whether reflink should be doing anything or not, that's a "xfs_refcountbt_init_cursor() gets called both outside and inside transactions" lockdep false positive case. The problem here is lockdep has seen this allocation from within a transaction, hence a GFP_NOFS allocation, and now it's seeing it in a GFP_KERNEL context. Also note that we have an active reference to this inode. So, because the reclaim annotations overload the interrupt level detections and it's seen the inode ilock been taken in reclaim ("interrupt") context, this triggers a reclaim context warning where it thinks it is unsafe to do this allocation in GFP_KERNEL context holding the inode ilock..." This sounds like a fundamental problem of the reclaim lock detection. It is really impossible to annotate such a special usecase IMHO unless the reclaim lockup detection is reworked completely. Until then it is much better to provide a way to add "I know what I am doing flag" and mark problematic places. This would prevent from abusing GFP_NOFS flag which has a runtime effect even on configurations which have lockdep disabled. Introduce __GFP_NOLOCKDEP flag which tells the lockdep gfp tracking to skip the current allocation request. While we are at it also make sure that the radix tree doesn't accidentaly override tags stored in the upper part of the gfp_mask. Link: http://lkml.kernel.org/r/20170306131408.9828-3-mhocko@kernel.org Signed-off-by: Michal Hocko <mhocko@suse.com> Suggested-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Dave Chinner <david@fromorbit.com> Cc: Theodore Ts'o <tytso@mit.edu> Cc: Chris Mason <clm@fb.com> Cc: David Sterba <dsterba@suse.cz> Cc: Jan Kara <jack@suse.cz> Cc: Brian Foster <bfoster@redhat.com> Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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 Nikolay Borisov
|
6d7225f0cc |
lockdep: teach lockdep about memalloc_noio_save
Patch series "scope GFP_NOFS api", v5. This patch (of 7): Commit |
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Linus Torvalds
|
2f34c1231b |
Merge tag 'drm-for-v4.12' of git://people.freedesktop.org/~airlied/linux
Pull drm u pdates from Dave Airlie: "This is the main drm pull request for v4.12. Apart from two fixes pulls, everything should have been in drm-next for at least 2 weeks. The biggest thing in here is AMD released the public headers for their upcoming VEGA GPUs. These as always are quite a sizeable chunk of header files. They've also added initial non-display support for those GPUs, though they aren't available in production yet. Otherwise it's pretty much normal. New bridge drivers: - megachips-stdpxxxx-ge-b850v3-fw LVDS->DP++ - generic LVDS bridge support. Core: - Displayport link train failure reporting to userspace - debugfs interface cleaned up - subsystem TODO in kerneldoc now - Extended fbdev support (flipping and vblank wait) - drm_platform removed - EDP CRC support in helper - HF-VSDB SCDC support in EDID parser - Lots of code cleanups and header extraction - Thunderbolt external GPU awareness - Atomic helper improvements - Documentation improvements panel: - Sitronix and Samsung new panel support amdgpu: - Preliminary vega10 support - Multi-level page table support - GPU sensor support for userspace - PRT support for sparse buffers - SR-IOV improvements - Non-contig VRAM CPU mapping i915: - Atomic modesetting enabled by default on Gen5+ - LSPCON improvements - Atomic state handling for cdclk - GPU reset improvements - In-kernel unit tests - Geminilake improvements and color manager support - Designware i2c fixes - vblank evasion improvements - Hotplug safe connector iterators - GVT scheduler QoS support - GVT Kabylake support nouveau: - Acceleration support for Pascal (GP10x). - Rearchitecture of code handling proprietary signed firmware - Fix GTX 970 with odd MMU configuration - GP10B support - GP107 acceleration support vmwgfx: - Atomic modesetting support for vmwgfx omapdrm: - Support for render nodes - Refactor omapdss code - Fix some probe ordering issues - Fix too dark RGB565 rendering sunxi: - prelim rework for multiple pipes. mali-dp: - Color management support - Plane scaling - Power management improvements imx-drm: - Prefetch Resolve Engine/Gasket on i.MX6QP - Deferred plane disabling - Separate alpha support mediatek: - Mediatek SoC MT2701 support rcar-du: - Gen3 HDMI support msm: - 4k support for newer chips - OPP bindings for gpu - prep work for per-process pagetables vc4: - HDMI audio support - fixes qxl: - minor fixes. dw-hdmi: - PHY improvements - CSC fixes - Amlogic GX SoC support" * tag 'drm-for-v4.12' of git://people.freedesktop.org/~airlied/linux: (1778 commits) drm/nouveau/fb/gf100-: Fix 32 bit wraparound in new ram detection drm/nouveau/secboot/gm20b: fix the error return code in gm20b_secboot_tegra_read_wpr() drm/nouveau/kms: Increase max retries in scanout position queries. drm/nouveau/bios/bitP: check that table is long enough for optional pointers drm/nouveau/fifo/nv40: no ctxsw for pre-nv44 mpeg engine drm: mali-dp: use div_u64 for expensive 64-bit divisions drm/i915: Confirm the request is still active before adding it to the await drm/i915: Avoid busy-spinning on VLV_GLTC_PW_STATUS mmio drm/i915/selftests: Allocate inode/file dynamically drm/i915: Fix system hang with EI UP masked on Haswell drm/i915: checking for NULL instead of IS_ERR() in mock selftests drm/i915: Perform link quality check unconditionally during long pulse drm/i915: Fix use after free in lpe_audio_platdev_destroy() drm/i915: Use the right mapping_gfp_mask for final shmem allocation drm/i915: Make legacy cursor updates more unsynced drm/i915: Apply a cond_resched() to the saturated signaler drm/i915: Park the signaler before sleeping drm: mali-dp: Check the mclk rate and allow up/down scaling drm: mali-dp: Enable image enhancement when scaling drm: mali-dp: Add plane upscaling support ... |
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Linus Torvalds
|
207fb8c304 |
Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Ingo Molnar:
"The main changes in this cycle were:
- a big round of FUTEX_UNLOCK_PI improvements, fixes, cleanups and
general restructuring
- lockdep updates such as new checks for lock_downgrade()
- introduce the new atomic_try_cmpxchg() locking API and use it to
optimize refcount code generation
- ... plus misc fixes, updates and cleanups"
* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (38 commits)
MAINTAINERS: Add FUTEX SUBSYSTEM
futex: Clarify mark_wake_futex memory barrier usage
futex: Fix small (and harmless looking) inconsistencies
futex: Avoid freeing an active timer
rtmutex: Plug preempt count leak in rt_mutex_futex_unlock()
rtmutex: Fix more prio comparisons
rtmutex: Fix PI chain order integrity
sched,tracing: Update trace_sched_pi_setprio()
sched/rtmutex: Refactor rt_mutex_setprio()
rtmutex: Clean up
sched/deadline/rtmutex: Dont miss the dl_runtime/dl_period update
sched/rtmutex/deadline: Fix a PI crash for deadline tasks
rtmutex: Deboost before waking up the top waiter
locking/ww-mutex: Limit stress test to 2 seconds
locking/atomic: Fix atomic_try_cmpxchg() semantics
lockdep: Fix per-cpu static objects
futex: Drop hb->lock before enqueueing on the rtmutex
futex: Futex_unlock_pi() determinism
futex: Rework futex_lock_pi() to use rt_mutex_*_proxy_lock()
futex,rt_mutex: Restructure rt_mutex_finish_proxy_lock()
...
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 Ingo Molnar
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58d30c36d4 |
Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu
Pull RCU updates from Paul E. McKenney: - Documentation updates. - Miscellaneous fixes. - Parallelize SRCU callback handling (plus overlapping patches). Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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 Paul E. McKenney
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a5dd63efda |
lockdep: Use "WARNING" tag on lockdep splats
This commit changes lockdep splats to begin lines with "WARNING" and to use pr_warn() instead of printk(). This change eases scripted analysis of kernel console output. Reported-by: Dmitry Vyukov <dvyukov@google.com> Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Dmitry Vyukov <dvyukov@google.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org> |
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 Daniel Jordan
|
395102db44 |
sparc64: Use LOCKDEP_SMALL, not PROVE_LOCKING_SMALL
CONFIG_PROVE_LOCKING_SMALL shrinks the memory usage of lockdep so the
kernel text, data, and bss fit in the required 32MB limit, but this
option is not set for every config that enables lockdep.
A 4.10 kernel fails to boot with the console output
Kernel: Using 8 locked TLB entries for main kernel image.
hypervisor_tlb_lock[2000000:0:8000000071c007c3:1]: errors with f
Program terminated
with these config options
CONFIG_LOCKDEP=y
CONFIG_LOCK_STAT=y
CONFIG_PROVE_LOCKING=n
To fix, rename CONFIG_PROVE_LOCKING_SMALL to CONFIG_LOCKDEP_SMALL, and
enable this option with CONFIG_LOCKDEP=y so we get the reduced memory
usage every time lockdep is turned on.
Tested that CONFIG_LOCKDEP_SMALL is set to 'y' if and only if
CONFIG_LOCKDEP is set to 'y'. When other lockdep-related config options
that select CONFIG_LOCKDEP are enabled (e.g. CONFIG_LOCK_STAT or
CONFIG_PROVE_LOCKING), verified that CONFIG_LOCKDEP_SMALL is also
enabled.
Fixes:
|
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 Mike Galbraith
|
def34eaae5 |
rtmutex: Plug preempt count leak in rt_mutex_futex_unlock()
mark_wakeup_next_waiter() already disables preemption, doing so again
leaves us with an unpaired preempt_disable().
Fixes:
|
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Peter Zijlstra
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19830e5524 |
rtmutex: Fix more prio comparisons
There was a pure ->prio comparison left in try_to_wake_rt_mutex(), convert it to use rt_mutex_waiter_less(), noting that greater-or-equal is not-less (both in kernel priority view). This necessitated the introduction of cmp_task() which creates a pointer to an unnamed stack variable of struct rt_mutex_waiter type to compare against tasks. With this, we can now also create and employ rt_mutex_waiter_equal(). Reviewed-and-tested-by: Juri Lelli <juri.lelli@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: juri.lelli@arm.com Cc: bigeasy@linutronix.de Cc: xlpang@redhat.com Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: jdesfossez@efficios.com Cc: bristot@redhat.com Link: http://lkml.kernel.org/r/20170323150216.455584638@infradead.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
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Peter Zijlstra
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e0aad5b44f |
rtmutex: Fix PI chain order integrity
rt_mutex_waiter::prio is a copy of task_struct::prio which is updated during the PI chain walk, such that the PI chain order isn't messed up by (asynchronous) task state updates. Currently rt_mutex_waiter_less() uses task state for deadline tasks; this is broken, since the task state can, as said above, change asynchronously, causing the RB tree order to change without actual tree update -> FAIL. Fix this by also copying the deadline into the rt_mutex_waiter state and updating it along with its prio field. Ideally we would also force PI chain updates whenever DL tasks update their deadline parameter, but for first approximation this is less broken than it was. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: juri.lelli@arm.com Cc: bigeasy@linutronix.de Cc: xlpang@redhat.com Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: jdesfossez@efficios.com Cc: bristot@redhat.com Link: http://lkml.kernel.org/r/20170323150216.403992539@infradead.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
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Peter Zijlstra
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acd58620e4 |
sched/rtmutex: Refactor rt_mutex_setprio()
With the introduction of SCHED_DEADLINE the whole notion that priority is a single number is gone, therefore the @prio argument to rt_mutex_setprio() doesn't make sense anymore. So rework the code to pass a pi_task instead. Note this also fixes a problem with pi_top_task caching; previously we would not set the pointer (call rt_mutex_update_top_task) if the priority didn't change, this could lead to a stale pointer. As for the XXX, I think its fine to use pi_task->prio, because if it differs from waiter->prio, a PI chain update is immenent. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: juri.lelli@arm.com Cc: bigeasy@linutronix.de Cc: xlpang@redhat.com Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: jdesfossez@efficios.com Cc: bristot@redhat.com Link: http://lkml.kernel.org/r/20170323150216.303827095@infradead.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
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Peter Zijlstra
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aa2bfe5536 |
rtmutex: Clean up
Previous patches changed the meaning of the return value of rt_mutex_slowunlock(); update comments and code to reflect this. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: juri.lelli@arm.com Cc: bigeasy@linutronix.de Cc: xlpang@redhat.com Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: jdesfossez@efficios.com Cc: bristot@redhat.com Link: http://lkml.kernel.org/r/20170323150216.255058238@infradead.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
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 Xunlei Pang
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85e2d4f992 |
sched/deadline/rtmutex: Dont miss the dl_runtime/dl_period update
Currently dl tasks will actually return at the very beginning
of rt_mutex_adjust_prio_chain() in !detect_deadlock cases:
if (waiter->prio == task->prio) {
if (!detect_deadlock)
goto out_unlock_pi; // out here
else
requeue = false;
}
As the deadline value of blocked deadline tasks(waiters) without
changing their sched_class(thus prio doesn't change) never changes,
this seems reasonable, but it actually misses the chance of updating
rt_mutex_waiter's "dl_runtime(period)_copy" if a waiter updates its
deadline parameters(dl_runtime, dl_period) or boosted waiter changes
to !deadline class.
Thus, force deadline task not out by adding the !dl_prio() condition.
Signed-off-by: Xunlei Pang <xlpang@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: juri.lelli@arm.com
Cc: bigeasy@linutronix.de
Cc: mathieu.desnoyers@efficios.com
Cc: jdesfossez@efficios.com
Cc: bristot@redhat.com
Link: http://lkml.kernel.org/r/1460633827-345-7-git-send-email-xlpang@redhat.com
Link: http://lkml.kernel.org/r/20170323150216.206577901@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Xunlei Pang
|
e96a7705e7 |
sched/rtmutex/deadline: Fix a PI crash for deadline tasks
A crash happened while I was playing with deadline PI rtmutex.
BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
IP: [<ffffffff810eeb8f>] rt_mutex_get_top_task+0x1f/0x30
PGD 232a75067 PUD 230947067 PMD 0
Oops: 0000 [#1] SMP
CPU: 1 PID: 10994 Comm: a.out Not tainted
Call Trace:
[<ffffffff810b658c>] enqueue_task+0x2c/0x80
[<ffffffff810ba763>] activate_task+0x23/0x30
[<ffffffff810d0ab5>] pull_dl_task+0x1d5/0x260
[<ffffffff810d0be6>] pre_schedule_dl+0x16/0x20
[<ffffffff8164e783>] __schedule+0xd3/0x900
[<ffffffff8164efd9>] schedule+0x29/0x70
[<ffffffff8165035b>] __rt_mutex_slowlock+0x4b/0xc0
[<ffffffff81650501>] rt_mutex_slowlock+0xd1/0x190
[<ffffffff810eeb33>] rt_mutex_timed_lock+0x53/0x60
[<ffffffff810ecbfc>] futex_lock_pi.isra.18+0x28c/0x390
[<ffffffff810ed8b0>] do_futex+0x190/0x5b0
[<ffffffff810edd50>] SyS_futex+0x80/0x180
This is because rt_mutex_enqueue_pi() and rt_mutex_dequeue_pi()
are only protected by pi_lock when operating pi waiters, while
rt_mutex_get_top_task(), will access them with rq lock held but
not holding pi_lock.
In order to tackle it, we introduce new "pi_top_task" pointer
cached in task_struct, and add new rt_mutex_update_top_task()
to update its value, it can be called by rt_mutex_setprio()
which held both owner's pi_lock and rq lock. Thus "pi_top_task"
can be safely accessed by enqueue_task_dl() under rq lock.
Originally-From: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Xunlei Pang <xlpang@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: juri.lelli@arm.com
Cc: bigeasy@linutronix.de
Cc: mathieu.desnoyers@efficios.com
Cc: jdesfossez@efficios.com
Cc: bristot@redhat.com
Link: http://lkml.kernel.org/r/20170323150216.157682758@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Xunlei Pang
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2a1c602994 |
rtmutex: Deboost before waking up the top waiter
We should deboost before waking the high-priority task, such that we don't run two tasks with the same "state" (priority, deadline, sched_class, etc). In order to make sure the boosting task doesn't start running between unlock and deboost (due to 'spurious' wakeup), we move the deboost under the wait_lock, that way its serialized against the wait loop in __rt_mutex_slowlock(). Doing the deboost early can however lead to priority-inversion if current would get preempted after the deboost but before waking our high-prio task, hence we disable preemption before doing deboost, and enabling it after the wake up is over. This gets us the right semantic order, but most importantly however; this change ensures pointer stability for the next patch, where we have rt_mutex_setprio() cache a pointer to the top-most waiter task. If we, as before this change, do the wakeup first and then deboost, this pointer might point into thin air. [peterz: Changelog + patch munging] Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Xunlei Pang <xlpang@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: juri.lelli@arm.com Cc: bigeasy@linutronix.de Cc: mathieu.desnoyers@efficios.com Cc: jdesfossez@efficios.com Cc: bristot@redhat.com Link: http://lkml.kernel.org/r/20170323150216.110065320@infradead.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
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 Chris Wilson
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57dd924e54 |
locking/ww-mutex: Limit stress test to 2 seconds
Use a timeout rather than a fixed number of loops to avoid running for very long periods, such as under the kbuilder VMs. Reported-by: kernel test robot <xiaolong.ye@intel.com> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20170310105733.6444-1-chris@chris-wilson.co.uk Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Peter Zijlstra
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56222b212e |
futex: Drop hb->lock before enqueueing on the rtmutex
When PREEMPT_RT_FULL does the spinlock -> rt_mutex substitution the PI
chain code will (falsely) report a deadlock and BUG.
The problem is that it hold hb->lock (now an rt_mutex) while doing
task_blocks_on_rt_mutex on the futex's pi_state::rtmutex. This, when
interleaved just right with futex_unlock_pi() leads it to believe to see an
AB-BA deadlock.
Task1 (holds rt_mutex, Task2 (does FUTEX_LOCK_PI)
does FUTEX_UNLOCK_PI)
lock hb->lock
lock rt_mutex (as per start_proxy)
lock hb->lock
Which is a trivial AB-BA.
It is not an actual deadlock, because it won't be holding hb->lock by the
time it actually blocks on the rt_mutex, but the chainwalk code doesn't
know that and it would be a nightmare to handle this gracefully.
To avoid this problem, do the same as in futex_unlock_pi() and drop
hb->lock after acquiring wait_lock. This still fully serializes against
futex_unlock_pi(), since adding to the wait_list does the very same lock
dance, and removing it holds both locks.
Aside of solving the RT problem this makes the lock and unlock mechanism
symetric and reduces the hb->lock held time.
Reported-and-tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: juri.lelli@arm.com
Cc: xlpang@redhat.com
Cc: rostedt@goodmis.org
Cc: mathieu.desnoyers@efficios.com
Cc: jdesfossez@efficios.com
Cc: dvhart@infradead.org
Cc: bristot@redhat.com
Link: http://lkml.kernel.org/r/20170322104152.161341537@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Peter Zijlstra
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cfafcd117d |
futex: Rework futex_lock_pi() to use rt_mutex_*_proxy_lock()
By changing futex_lock_pi() to use rt_mutex_*_proxy_lock() all wait_list modifications are done under both hb->lock and wait_lock. This closes the obvious interleave pattern between futex_lock_pi() and futex_unlock_pi(), but not entirely so. See below: Before: futex_lock_pi() futex_unlock_pi() unlock hb->lock lock hb->lock unlock hb->lock lock rt_mutex->wait_lock unlock rt_mutex_wait_lock -EAGAIN lock rt_mutex->wait_lock list_add unlock rt_mutex->wait_lock schedule() lock rt_mutex->wait_lock list_del unlock rt_mutex->wait_lock <idem> -EAGAIN lock hb->lock After: futex_lock_pi() futex_unlock_pi() lock hb->lock lock rt_mutex->wait_lock list_add unlock rt_mutex->wait_lock unlock hb->lock schedule() lock hb->lock unlock hb->lock lock hb->lock lock rt_mutex->wait_lock list_del unlock rt_mutex->wait_lock lock rt_mutex->wait_lock unlock rt_mutex_wait_lock -EAGAIN unlock hb->lock It does however solve the earlier starvation/live-lock scenario which got introduced with the -EAGAIN since unlike the before scenario; where the -EAGAIN happens while futex_unlock_pi() doesn't hold any locks; in the after scenario it happens while futex_unlock_pi() actually holds a lock, and then it is serialized on that lock. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: juri.lelli@arm.com Cc: bigeasy@linutronix.de Cc: xlpang@redhat.com Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: jdesfossez@efficios.com Cc: dvhart@infradead.org Cc: bristot@redhat.com Link: http://lkml.kernel.org/r/20170322104152.062785528@infradead.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
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Peter Zijlstra
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38d589f2fd |
futex,rt_mutex: Restructure rt_mutex_finish_proxy_lock()
With the ultimate goal of keeping rt_mutex wait_list and futex_q waiters consistent it's necessary to split 'rt_mutex_futex_lock()' into finer parts, such that only the actual blocking can be done without hb->lock held. Split split_mutex_finish_proxy_lock() into two parts, one that does the blocking and one that does remove_waiter() when the lock acquire failed. When the rtmutex was acquired successfully the waiter can be removed in the acquisiton path safely, since there is no concurrency on the lock owner. This means that, except for futex_lock_pi(), all wait_list modifications are done with both hb->lock and wait_lock held. [bigeasy@linutronix.de: fix for futex_requeue_pi_signal_restart] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: juri.lelli@arm.com Cc: bigeasy@linutronix.de Cc: xlpang@redhat.com Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: jdesfossez@efficios.com Cc: dvhart@infradead.org Cc: bristot@redhat.com Link: http://lkml.kernel.org/r/20170322104152.001659630@infradead.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
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Peter Zijlstra
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50809358dd |
futex,rt_mutex: Introduce rt_mutex_init_waiter()
Since there's already two copies of this code, introduce a helper now before adding a third one. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: juri.lelli@arm.com Cc: bigeasy@linutronix.de Cc: xlpang@redhat.com Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: jdesfossez@efficios.com Cc: dvhart@infradead.org Cc: bristot@redhat.com Link: http://lkml.kernel.org/r/20170322104151.950039479@infradead.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
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Peter Zijlstra
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5293c2efda |
futex,rt_mutex: Provide futex specific rt_mutex API
Part of what makes futex_unlock_pi() intricate is that rt_mutex_futex_unlock() -> rt_mutex_slowunlock() can drop rt_mutex::wait_lock. This means it cannot rely on the atomicy of wait_lock, which would be preferred in order to not rely on hb->lock so much. The reason rt_mutex_slowunlock() needs to drop wait_lock is because it can race with the rt_mutex fastpath, however futexes have their own fast path. Since futexes already have a bunch of separate rt_mutex accessors, complete that set and implement a rt_mutex variant without fastpath for them. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: juri.lelli@arm.com Cc: bigeasy@linutronix.de Cc: xlpang@redhat.com Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: jdesfossez@efficios.com Cc: dvhart@infradead.org Cc: bristot@redhat.com Link: http://lkml.kernel.org/r/20170322104151.702962446@infradead.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |