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del_timer_sync() buys nothing for cancel_delayed_work(), but it is less
efficient since it locks the timer unconditionally, and may wait for the
completion of the delayed_work_timer_fn().
cancel_delayed_work() == 0 means:
before this patch:
work->func may still be running or queued
after this patch:
work->func may still be running or queued, or
delayed_work_timer_fn->__queue_work() in progress.
The latter doesn't differ from the caller's POV,
delayed_work_timer_fn() is called with _PENDING
bit set.
cancel_delayed_work() == 1 with this patch adds a new possibility:
delayed_work->work was cancelled, but delayed_work_timer_fn
is still running (this is only possible for the re-arming
works on single-threaded workqueue).
In this case the timer was re-started by work->func(), nobody
else can do this. This in turn means that delayed_work_timer_fn
has already passed __queue_work() (and wont't touch delayed_work)
because nobody else can queue delayed_work->work.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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On architectures where the atomicity of the bit operations is handled by
external means (ie a separate spinlock to protect concurrent accesses),
just doing a direct assignment on the workqueue data field (as done by
commit 4594bf159f1962cec3b727954b7c598b07e2e737) can cause the
assignment to be lost due to lack of serialization with the bitops on
the same word.
So we need to serialize the assignment with the locks on those
architectures (notably older ARM chips, PA-RISC and sparc32).
So rather than using an "unsigned long", let's use "atomic_long_t",
which already has a safe assignment operation (atomic_long_set()) on
such architectures.
This requires that the atomic operations use the same atomicity locks as
the bit operations do, but that is largely the case anyway. Sparc32
will probably need fixing.
Architectures (including modern ARM with LL/SC) that implement sane
atomic operations for SMP won't see any of this matter.
Cc: Russell King <rmk+lkml@arm.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: David Miller <davem@davemloft.com>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Linux Arch Maintainers <linux-arch@vger.kernel.org>
Cc: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Nobody uses it, but it was still wrong. Using the macro argument name
'work' meant that when we used 'work' as a member name, that would also
get replaced by the macro argument.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This allows workqueue users to run just their own pending work, rather
than wait for the whole workqueue to finish running. This solves the
deadlock with networking libphy that was due to other workqueue entries
possibly needing a lock that was held by the routine that wanted to
flush its own work.
It's not wonderful: if you absolutely need to synchronize with the work
function having been executed, any user strictly speaking should have
its own completion tracking logic, since when we run things explicitly
by hand, the generic workqueue layer can no longer help us synchronize.
Also, this is strictly only usable for work that has been scheduled
without any delayed timers. You can not mix the new interface with
schedule_delayed_work().
But it's better than what we had currently.
Acked-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Make it possible to create a workqueue the worker thread of which will be
frozen during suspend, along with other kernel threads.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Cc: Nigel Cunningham <nigel@suspend2.net>
Cc: David Chinner <dgc@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Pass the work_struct pointer to the work function rather than context data.
The work function can use container_of() to work out the data.
For the cases where the container of the work_struct may go away the moment the
pending bit is cleared, it is made possible to defer the release of the
structure by deferring the clearing of the pending bit.
To make this work, an extra flag is introduced into the management side of the
work_struct. This governs auto-release of the structure upon execution.
Ordinarily, the work queue executor would release the work_struct for further
scheduling or deallocation by clearing the pending bit prior to jumping to the
work function. This means that, unless the driver makes some guarantee itself
that the work_struct won't go away, the work function may not access anything
else in the work_struct or its container lest they be deallocated.. This is a
problem if the auxiliary data is taken away (as done by the last patch).
However, if the pending bit is *not* cleared before jumping to the work
function, then the work function *may* access the work_struct and its container
with no problems. But then the work function must itself release the
work_struct by calling work_release().
In most cases, automatic release is fine, so this is the default. Special
initiators exist for the non-auto-release case (ending in _NAR).
Signed-Off-By: David Howells <dhowells@redhat.com>
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Reclaim a word from the size of the work_struct by folding the pending bit and
the wq_data pointer together. This shouldn't cause misalignment problems as
all pointers should be at least 4-byte aligned.
Signed-Off-By: David Howells <dhowells@redhat.com>
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Define a type for the work function prototype. It's not only kept in the
work_struct struct, it's also passed as an argument to several functions.
This makes it easier to change it.
Signed-Off-By: David Howells <dhowells@redhat.com>
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Separate delayable work items from non-delayable work items be splitting them
into a separate structure (delayed_work), which incorporates a work_struct and
the timer_list removed from work_struct.
The work_struct struct is huge, and this limits it's usefulness. On a 64-bit
architecture it's nearly 100 bytes in size. This reduces that by half for the
non-delayable type of event.
Signed-Off-By: David Howells <dhowells@redhat.com>
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Add queue_delayed_work_on() interface for workqueues.
Signed-off-by: Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Dave Jones <davej@redhat.com>
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We have several points in the SCSI stack (primarily for our device
functions) where we need to guarantee process context, but (given the
place where the last reference was released) we cannot guarantee this.
This API gets around the issue by executing the function directly if
the caller has process context, but scheduling a workqueue to execute
in process context if the caller doesn't have it.
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
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swap migration's isolate_lru_page() currently uses an IPI to notify other
processors that the lru caches need to be drained if the page cannot be
found on the LRU. The IPI interrupt may interrupt a processor that is just
processing lru requests and cause a race condition.
This patch introduces a new function run_on_each_cpu() that uses the
keventd() to run the LRU draining on each processor. Processors disable
preemption when dealing the LRU caches (these are per processor) and thus
executing LRU draining from another process is safe.
Thanks to Lee Schermerhorn <lee.schermerhorn@hp.com> for finding this race
condition.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This was unexported by Arjan because we have no current users.
However, during a conversion from tasklets to workqueues of the parisc led
functions, we ran across a case where this was needed. In particular, the
open coded equivalent of cancel_rearming_delayed_workqueue was implemented
incorrectly, which is, I think, all the evidence necessary that this is a
useful API.
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
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