linux/kernel/async.c, branch v3.8

async: fix __lowest_in_progress()

2013-01-23T00:21:24Z

Commit 083b804c4d3e ("async: use workqueue for worker pool") made it possible that async jobs are moved from pending to running out-of-order. While pending async jobs will be queued and dispatched for execution in the same order, nothing guarantees they'll enter "1) move self to the running queue" of async_run_entry_fn() in the same order. Before the conversion, async implemented its own worker pool. An async worker, upon being woken up, fetches the first item from the pending list, which kept the executing lists sorted. The conversion to workqueue was done by adding work_struct to each async_entry and async just schedules the work item. The queueing and dispatching of such work items are still in order but now each worker thread is associated with a specific async_entry and moves that specific async_entry to the executing list. So, depending on which worker reaches that point earlier, which is non-deterministic, we may end up moving an async_entry with larger cookie before one with smaller one. This broke __lowest_in_progress(). running->domain may not be properly sorted and is not guaranteed to contain lower cookies than pending list when not empty. Fix it by ensuring sort-inserting to the running list and always looking at both pending and running when trying to determine the lowest cookie. Over time, the async synchronization implementation became quite messy. We better restructure it such that each async_entry is linked to two lists - one global and one per domain - and not move it when execution starts. There's no reason to distinguish pending and running. They behave the same for synchronization purposes. Signed-off-by: Tejun Heo Cc: Arjan van de Ven Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds

module, async: async_synchronize_full() on module init iff async is used

2013-01-16T17:05:33Z

If the default iosched is built as module, the kernel may deadlock while trying to load the iosched module on device probe if the probing was running off async. This is because async_synchronize_full() at the end of module init ends up waiting for the async job which initiated the module loading. async A modprobe 1. finds a device 2. registers the block device 3. request_module(default iosched) 4. modprobe in userland 5. load and init module 6. async_synchronize_full() Async A waits for modprobe to finish in request_module() and modprobe waits for async A to finish in async_synchronize_full(). Because there's no easy to track dependency once control goes out to userland, implementing properly nested flushing is difficult. For now, make module init perform async_synchronize_full() iff module init has queued async jobs as suggested by Linus. This avoids the described deadlock because iosched module doesn't use async and thus wouldn't invoke async_synchronize_full(). This is hacky and incomplete. It will deadlock if async module loading nests; however, this works around the known problem case and seems to be the best of bad options. For more details, please refer to the following thread. http://thread.gmane.org/gmane.linux.kernel/1420814 Signed-off-by: Tejun Heo Reported-by: Alex Riesen Tested-by: Ming Lei Tested-by: Alex Riesen Cc: Arjan van de Ven Cc: Jens Axboe Signed-off-by: Linus Torvalds

[SCSI] async: make async_synchronize_full() flush all work regardless of domain

2012-07-20T08:07:37Z

In response to an async related regression James noted: "My theory is that this is an init problem: The assumption in a lot of our code is that async_synchronize_full() waits for everything ... even the domain specific async schedules, which isn't true." ...so make this assumption true. Each domain, including the default one, registers itself on a global domain list when work is scheduled. Once all entries complete it exits that list. Waiting for the list to be empty syncs all in-flight work across all domains. Domains can opt-out of global syncing if they are declared as exclusive ASYNC_DOMAIN_EXCLUSIVE(). All stack-based domains have been declared exclusive since the domain may go out of scope as soon as the last work item completes. Statically declared domains are mostly ok, but async_unregister_domain() is there to close any theoretical races with pending async_synchronize_full waiters at module removal time. Signed-off-by: Dan Williams Acked-by: Arjan van de Ven Reported-by: Meelis Roos Reported-by: Eldad Zack Tested-by: Eldad Zack Signed-off-by: James Bottomley

[SCSI] async: introduce 'async_domain' type

2012-07-20T08:05:54Z

This is in preparation for teaching async_synchronize_full() to sync all pending async work, and not just on the async_running domain. This conversion is functionally equivalent, just embedding the existing list in a new async_domain type. The .registered attribute is used in a later patch to distinguish between domains that want to be flushed by async_synchronize_full() versus those that only expect async_synchronize_{full|cookie}_domain to be used for flushing. [jejb: add async.h to scsi_priv.h for struct async_domain] Signed-off-by: Dan Williams Acked-by: Arjan van de Ven Acked-by: Mark Brown Tested-by: Eldad Zack Signed-off-by: James Bottomley

kernel/async: remove redundant declaration.

2012-01-12T23:02:18Z

It's in linux/init.h, and I'm about to change it to a bool. Cc: Arjan van de Ven Signed-off-by: Rusty Russell

kernel: Map most files to use export.h instead of module.h

2011-10-31T13:20:12Z

The changed files were only including linux/module.h for the EXPORT_SYMBOL infrastructure, and nothing else. Revector them onto the isolated export header for faster compile times. Nothing to see here but a whole lot of instances of: -#include +#include This commit is only changing the kernel dir; next targets will probably be mm, fs, the arch dirs, etc. Signed-off-by: Paul Gortmaker

async: uninitialized warning corrections

2011-09-15T12:22:28Z

The variables here are really not used uninitialized. kernel/async.c: In function 'async_synchronize_cookie_domain': kernel/async.c:270:10: warning: 'starttime.tv64' may be used uninitialized in this function kernel/async.c: In function 'async_run_entry_fn': kernel/async.c:122:10: warning: 'calltime.tv64' may be used uninitialized in this function Signed-off-by: Vitaliy Ivanov Signed-off-by: Konstantin Khlebnikov Signed-off-by: Viresh Kumar Signed-off-by: Jiri Kosina

async: Fixed an include coding style issue

2011-06-15T02:48:46Z

Added , and Removed . Added KERN_DEBUG to printk() functions. Acked-by: Arjan van de Ven Signed-off-by: Paul McQuade Link: http://lkml.kernel.org/r/4DE596B4.7030904@gmail.com Signed-off-by: Steven Rostedt

async: use workqueue for worker pool

2010-07-14T09:29:46Z

Replace private worker pool with system_unbound_wq. Signed-off-by: Tejun Heo Acked-by: Arjan van de Ven

include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h

2010-03-30T13:02:32Z

percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo Guess-its-ok-by: Christoph Lameter Cc: Ingo Molnar Cc: Lee Schermerhorn