linux/kernel, branch v2.6.32

modules: don't export section names of empty sections via sysfs

2009-12-02T23:38:25Z

On the parisc architecture we face for each and every loaded kernel module this kernel "badness warning": sysfs: cannot create duplicate filename '/module/ac97_bus/sections/.text' Badness at fs/sysfs/dir.c:487 Reason for that is, that on parisc all kernel modules do have multiple .text sections due to the usage of the -ffunction-sections compiler flag which is needed to reach all jump targets on this platform. An objdump on such a kernel module gives: Sections: Idx Name Size VMA LMA File off Algn 0 .note.gnu.build-id 00000024 00000000 00000000 00000034 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 1 .text 00000000 00000000 00000000 00000058 2**0 CONTENTS, ALLOC, LOAD, READONLY, CODE 2 .text.ac97_bus_match 0000001c 00000000 00000000 00000058 2**2 CONTENTS, ALLOC, LOAD, READONLY, CODE 3 .text 00000000 00000000 00000000 000000d4 2**0 CONTENTS, ALLOC, LOAD, READONLY, CODE ... Since the .text sections are empty (size of 0 bytes) and won't be loaded by the kernel module loader anyway, I don't see a reason why such sections need to be listed under /sys/module//sections/ either. The attached patch does solve this issue by not exporting section names which are empty. This fixes bugzilla http://bugzilla.kernel.org/show_bug.cgi?id=14703 Signed-off-by: Helge Deller CC: rusty@rustcorp.com.au CC: akpm@linux-foundation.org CC: James.Bottomley@HansenPartnership.com CC: roland@redhat.com CC: dave@hiauly1.hia.nrc.ca Signed-off-by: Linus Torvalds

SLOW_WORK: Move slow_work's proc file to debugfs

2009-12-01T16:20:31Z

Move slow_work's debugging proc file to debugfs. Signed-off-by: David Howells Requested-and-acked-by: Ingo Molnar Signed-off-by: Linus Torvalds

SLOW_WORK: Fix the CONFIG_MODULES=n case

2009-12-01T15:35:11Z

Commits 3d7a641 ("SLOW_WORK: Wait for outstanding work items belonging to a module to clear") introduced some code to make sure that all of a module's slow-work items were complete before that module was removed, and commit 3bde31a ("SLOW_WORK: Allow a requeueable work item to sleep till the thread is needed") further extended that, breaking it in the process if CONFIG_MODULES=n: CC kernel/slow-work.o kernel/slow-work.c: In function 'slow_work_execute': kernel/slow-work.c:313: error: 'slow_work_thread_processing' undeclared (first use in this function) kernel/slow-work.c:313: error: (Each undeclared identifier is reported only once kernel/slow-work.c:313: error: for each function it appears in.) kernel/slow-work.c: In function 'slow_work_wait_for_items': kernel/slow-work.c:950: error: 'slow_work_unreg_sync_lock' undeclared (first use in this function) kernel/slow-work.c:951: error: 'slow_work_unreg_wq' undeclared (first use in this function) kernel/slow-work.c:961: error: 'slow_work_unreg_work_item' undeclared (first use in this function) kernel/slow-work.c:974: error: 'slow_work_unreg_module' undeclared (first use in this function) kernel/slow-work.c:977: error: 'slow_work_thread_processing' undeclared (first use in this function) make[1]: *** [kernel/slow-work.o] Error 1 Fix this by: (1) Extracting the bits of slow_work_execute() that are contingent on CONFIG_MODULES, and the bits that should be, into inline functions and placing them into the #ifdef'd section that defines the relevant variables and adding stubs for moduleless kernels. This allows the removal of some #ifdefs. (2) #ifdef'ing out the contents of slow_work_wait_for_items() in moduleless kernels. The four functions related to handling module unloading synchronisation (and their associated variables) could be offloaded into a separate .c file, but each function is only used once and three of them are tiny, so doing so would prevent them from being inlined. Reported-by: Ingo Molnar Signed-off-by: David Howells Signed-off-by: Linus Torvalds

SLOW_WORK: Allow a requeueable work item to sleep till the thread is needed

2009-11-19T18:10:57Z

Add a function to allow a requeueable work item to sleep till the thread processing it is needed by the slow-work facility to perform other work. Sometimes a work item can't progress immediately, but must wait for the completion of another work item that's currently being processed by another slow-work thread. In some circumstances, the waiting item could instead - theoretically - put itself back on the queue and yield its thread back to the slow-work facility, thus waiting till it gets processing time again before attempting to progress. This would allow other work items processing time on that thread. However, this only works if there is something on the queue for it to queue behind - otherwise it will just get a thread again immediately, and will end up cycling between the queue and the thread, eating up valuable CPU time. So, slow_work_sleep_till_thread_needed() is provided such that an item can put itself on a wait queue that will wake it up when the event it is actually interested in occurs, then call this function in lieu of calling schedule(). This function will then sleep until either the item's event occurs or another work item appears on the queue. If another work item is queued, but the item's event hasn't occurred, then the work item should requeue itself and yield the thread back to the slow-work facility by returning. This can be used by CacheFiles for an object that is being created on one thread to wait for an object being deleted on another thread where there is nothing on the queue for the creation to go and wait behind. As soon as an item appears on the queue that could be given thread time instead, CacheFiles can stick the creating object back on the queue and return to the slow-work facility - assuming the object deletion didn't also complete. Signed-off-by: David Howells

SLOW_WORK: Allow the work items to be viewed through a /proc file

2009-11-19T18:10:51Z

Allow the executing and queued work items to be viewed through a /proc file for debugging purposes. The contents look something like the following: THR PID ITEM ADDR FL MARK DESC === ===== ================ == ===== ========== 0 3005 ffff880023f52348 a 952ms FSC: OBJ17d3: LOOK 1 3006 ffff880024e33668 2 160ms FSC: OBJ17e5 OP60d3b: Write1/Store fl=2 2 3165 ffff8800296dd180 a 424ms FSC: OBJ17e4: LOOK 3 4089 ffff8800262c8d78 a 212ms FSC: OBJ17ea: CRTN 4 4090 ffff88002792bed8 2 388ms FSC: OBJ17e8 OP60d36: Write1/Store fl=2 5 4092 ffff88002a0ef308 2 388ms FSC: OBJ17e7 OP60d2e: Write1/Store fl=2 6 4094 ffff88002abaf4b8 2 132ms FSC: OBJ17e2 OP60d4e: Write1/Store fl=2 7 4095 ffff88002bb188e0 a 388ms FSC: OBJ17e9: CRTN vsq - ffff880023d99668 1 308ms FSC: OBJ17e0 OP60f91: Write1/EnQ fl=2 vsq - ffff8800295d1740 1 212ms FSC: OBJ16be OP4d4b6: Write1/EnQ fl=2 vsq - ffff880025ba3308 1 160ms FSC: OBJ179a OP58dec: Write1/EnQ fl=2 vsq - ffff880024ec83e0 1 160ms FSC: OBJ17ae OP599f2: Write1/EnQ fl=2 vsq - ffff880026618e00 1 160ms FSC: OBJ17e6 OP60d33: Write1/EnQ fl=2 vsq - ffff880025a2a4b8 1 132ms FSC: OBJ16a2 OP4d583: Write1/EnQ fl=2 vsq - ffff880023cbe6d8 9 212ms FSC: OBJ17eb: LOOK vsq - ffff880024d37590 9 212ms FSC: OBJ17ec: LOOK vsq - ffff880027746cb0 9 212ms FSC: OBJ17ed: LOOK vsq - ffff880024d37ae8 9 212ms FSC: OBJ17ee: LOOK vsq - ffff880024d37cb0 9 212ms FSC: OBJ17ef: LOOK vsq - ffff880025036550 9 212ms FSC: OBJ17f0: LOOK vsq - ffff8800250368e0 9 212ms FSC: OBJ17f1: LOOK vsq - ffff880025036aa8 9 212ms FSC: OBJ17f2: LOOK In the 'THR' column, executing items show the thread they're occupying and queued threads indicate which queue they're on. 'PID' shows the process ID of a slow-work thread that's executing something. 'FL' shows the work item flags. 'MARK' indicates how long since an item was queued or began executing. Lastly, the 'DESC' column permits the owner of an item to give some information. Signed-off-by: David Howells

SLOW_WORK: Add delayed_slow_work support

2009-11-19T18:10:47Z

This adds support for starting slow work with a delay, similar to the functionality we have for workqueues. Signed-off-by: Jens Axboe Signed-off-by: David Howells

SLOW_WORK: Add support for cancellation of slow work

2009-11-19T18:10:43Z

Add support for cancellation of queued slow work and delayed slow work items. The cancellation functions will wait for items that are pending or undergoing execution to be discarded by the slow work facility. Attempting to enqueue work that is in the process of being cancelled will result in ECANCELED. Signed-off-by: Jens Axboe Signed-off-by: David Howells

SLOW_WORK: Make slow_work_ops ->get_ref/->put_ref optional

2009-11-19T18:10:39Z

Make the ability for the slow-work facility to take references on a work item optional as not everyone requires this. Even the internal slow-work stubs them out, so those can be got rid of too. Signed-off-by: Jens Axboe Signed-off-by: David Howells

SLOW_WORK: Wait for outstanding work items belonging to a module to clear

2009-11-19T18:10:23Z

Wait for outstanding slow work items belonging to a module to clear when unregistering that module as a user of the facility. This prevents the put_ref code of a work item from being taken away before it returns. Signed-off-by: David Howells

workqueue: fix race condition in schedule_on_each_cpu()

2009-11-18T01:40:33Z

Commit 65a64464349883891e21e74af16c05d6e1eeb4e9 ("HWPOISON: Allow schedule_on_each_cpu() from keventd") which allows schedule_on_each_cpu() to be called from keventd added a race condition. schedule_on_each_cpu() may race with cpu hotplug and end up executing the function twice on a cpu. Fix it by moving direct execution into the section protected with get/put_online_cpus(). While at it, update code such that direct execution is done after works have been scheduled for all other cpus and drop unnecessary cpu != orig test from flush loop. Signed-off-by: Tejun Heo Cc: Andi Kleen Acked-by: Oleg Nesterov Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds