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commit 777c6c5f1f6e757ae49ecca2ed72d6b1f523c007 upstream.
With exclusive waiters, every process woken up through the wait queue must
ensure that the next waiter down the line is woken when it has finished.
Interruptible waiters don't do that when aborting due to a signal. And if
an aborting waiter is concurrently woken up through the waitqueue, noone
will ever wake up the next waiter.
This has been observed with __wait_on_bit_lock() used by
lock_page_killable(): the first contender on the queue was aborting when
the actual lock holder woke it up concurrently. The aborted contender
didn't acquire the lock and therefor never did an unlock followed by
waking up the next waiter.
Add abort_exclusive_wait() which removes the process' wait descriptor from
the waitqueue, iff still queued, or wakes up the next waiter otherwise.
It does so under the waitqueue lock. Racing with a wake up means the
aborting process is either already woken (removed from the queue) and will
wake up the next waiter, or it will remove itself from the queue and the
concurrent wake up will apply to the next waiter after it.
Use abort_exclusive_wait() in __wait_event_interruptible_exclusive() and
__wait_on_bit_lock() when they were interrupted by other means than a wake
up through the queue.
[akpm@linux-foundation.org: coding-style fixes]
Reported-by: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Mentored-by: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Chuck Lever <cel@citi.umich.edu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Also move wake_up_locked() to be with the related functions
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
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Signed-off-by: Michael Opdenacker <michael@free-electrons.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
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allyesconfig vmlinux size delta:
text data bss dec filename
20736884 6073834 3075176 29885894 vmlinux.before
20721009 6073966 3075176 29870151 vmlinux.after
~18 bytes per callsite, 15K of text size (~0.1%) saved.
(as an added bonus this also removes a lockdep annotation.)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Create one lock class for all waitqueue locks in the kernel. Has no effect on
non-lockdep kernels.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Signed-off-by: Jörn Engel <joern@wohnheim.fh-wedel.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
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Document the requirement to use a memory barrier prior to wake_up_bit().
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Some of the parameters to __wait_on_bit() and __wait_on_bit_lock() are
redundant, as the wait_bit_queue parameter holds the flags word and the bit
number. This patch updates __wait_on_bit() and __wait_on_bit_lock() to
fetch that information from the wait_bit_queue passed to them and so reduce
the number of parameters so that -mregparm may be more effective.
Incremental atop the complete out-of-lining of the contention cases and the
fastcall and wait_on_bit_lock()/test_and_set_bit() fixes.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Move the slow paths of wait_on_bit() and wait_on_bit_lock() out of line.
Also uninline wake_up_bit() to reduce the number of callsites generated,
and adjust loop startup in __wait_on_bit_lock() to properly reflect its
usage in the contention case.
Incremental atop the fastcall and wait_on_bit_lock()/test_and_set_bit()
fixes. Successfully tested on x86-64.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Eliminate the inode waitqueue hashtable using bit_waitqueue() via
wait_on_bit() and wake_up_bit() to locate the waitqueue head associated
with a bit.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Eliminate the bh waitqueue hashtable using bit_waitqueue() via
wait_on_bit() and wake_up_bit() to locate the waitqueue head associated
with a bit.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Consolidate bit waiting code patterns for page waitqueues using
__wait_on_bit() and __wait_on_bit_lock().
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Eliminate specialized page and bh waitqueue hashing structures in favor of
a standardized structure, using wake_up_bit() to wake waiters using the
standardized wait_bit_key structure.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The following patch series consolidates the various instances of waitqueue
hashing to use a uniform structure and share the per-zone hashtable among all
waitqueue hashers. This is expected to increase the number of hashtable
buckets available for waiting on bh's and inodes and eliminate statically
allocated kernel data structures for greater node locality and reduced kernel
image size. Some attempt was made to look similar to Oleg Nesterov's
suggested API in order to provide some kind of credit for independent
invention of something very similar (the original versions of these patches
predated my public postings on the subject of filtered waitqueues).
These patches have the further benefit and intention of enabling aio to use
filtered wakeups by standardizing the data structure passed to wake functions
so that embedded waitqueue elements in aio structures may be succesfully
passed to the filtered wakeup wake functions, though this patch series doesn't
implement that particular functionality.
Successfully stress-tested on x86-64, and ia64 in recent prior versions.
This patch:
Move waitqueue -related functions not needing static functions in sched.c
to kernel/wait.c
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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