- 06 Jun, 2014 40 commits
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Rik van Riel authored
Some sysrq handlers can run for a long time, because they dump a lot of data onto a serial console. Having RCU stall warnings pop up in the middle of them only makes the problem worse. This patch temporarily disables RCU stall warnings while a sysrq request is handled. Signed-off-by:
Rik van Riel <riel@redhat.com> Suggested-by:
Paul McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Rik van Riel authored
Echoing values into /proc/sysrq-trigger seems to be a popular way to get information out of the kernel. However, dumping information about thousands of processes, or hundreds of CPUs to serial console can result in IRQs being blocked for minutes, resulting in various kinds of cascade failures. The most common failure is due to interrupts being blocked for a very long time. This can lead to things like failed IO requests, and other things the system cannot easily recover from. This problem is easily fixable by making __handle_sysrq use RCU instead of spin_lock_irqsave. This leaves the warning that RCU grace periods have not elapsed for a long time, but the system will come back from that automatically. It also leaves sysrq-from-irq-context when the sysrq keys are pressed, but that is probably desired since people want that to work in situations where the system is already hosed. The callers of register_sysrq_key and unregister_sysrq_key appear to be capable of sleeping. Signed-off-by:
Madper Xie <cxie@redhat.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Richard Weinberger <richard@nod.at> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by:
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Fabian Frederick authored
__constant_cpu_to_le32 converted to cpu_to_le32 Signed-off-by:
Fabian Frederick <fabf@skynet.be> Cc: Jeff Mahoney <jeffm@suse.com> Signed-off-by:
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Fabian Frederick authored
-Trivial code clean-up -Fix endif }; (coccinelle warning) Signed-off-by:
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Davidlohr Bueso authored
Performing vma lookups without taking the mm->mmap_sem is asking for trouble. While doing the search, the vma in question can be modified or even removed before returning to the caller. Take the lock (shared) in order to avoid races while iterating through the vmacache and/or rbtree. Signed-off-by:
Davidlohr Bueso <davidlohr@hp.com> Cc: Steven Miao <realmz6@gmail.com> Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
Joe Perches <joe@perches.com> Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Joe Perches authored
This typedef is unnecessary and should just be removed. Signed-off-by:
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Fabian Frederick authored
+ fix small typo Signed-off-by:
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Manfred Spraul authored
The actual Linux implementation for semctl(GETNCNT) and semctl(GETZCNT) always (since 0.99.10) reported a thread as sleeping on all semaphores that are listed in the semop() call. The documented behavior (both in the Linux man page and in the Single Unix Specification) is that a task should be reported on exactly one semaphore: The semaphore that caused the thread to got to sleep. This patch adds a pr_info_once() that is triggered if a thread hits the relevant case. The code triggers slightly too often, otherwise it would be necessary to replicate the old code. As there are no known users of GETNCNT or GETZCNT, this is done to prevent unnecessary bloat. The task that triggered is reported with name (tsk->comm) and pid. Signed-off-by:
Manfred Spraul <manfred@colorfullife.com> Acked-by:
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Manfred Spraul authored
SUSv4 clearly defines how semncnt and semzcnt must be calculated: A task waits on exactly one semaphore: The semaphore from the first operation in the sop array that cannot proceed. The Linux implementation never followed the standard, it tried to count all semaphores that might be the reason why a task sleeps. This patch fixes that. Note: a) The implementation assumes that GETNCNT and GETZCNT are rare operations, therefore the code counts them only on demand. (If they wouldn't be rare, then the non-compliance would have been found earlier) b) compared to the initial version of the patch, the BUG_ONs were removed and it was clarified that the new behavior conforms to SUS. Back-compatibility concerns: Manfred: : - there is no application in Fedora that uses GETNCNT or GETZCNT. : : - application that use only single-sop semop() are also safe, the : difference only affects complex apps. : : - portable application are also safe, the new behavior is standard : compliant. : : But that's it. The old behavior existed in Linux from 0.99.something : until now. Michael: : * These operations seem to be very little used. Grepping the public : source that is contained Fedora 20 source DVD, there appear to be no : uses. Of course, this says nothing about uses in private / : non-mainstream FOSS code, but it seems likely that the same pattern : is followed there. : : * The existing behavior is hard enough to understand that I suspect : that no one understood it well enough to rely on it anyway : (especially as that behavior contradicted both man page and POSIX). : : So, there's a chance of breakage, but I estimate that it's minute. Signed-off-by:
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Manfred Spraul authored
Preparation for the next patch: In the slow-path of perform_atomic_semop(), store a pointer to the operation that caused the operation to block. Signed-off-by:
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Manfred Spraul authored
Right now, perform_atomic_semop gets the content of sem_queue as individual fields. Changes that, instead pass a pointer to sem_queue. This is a preparation for the next patch: it uses sem_queue to store the reason why a task must sleep. Signed-off-by:
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Manfred Spraul authored
count_semzcnt and count_semncnt are more of less identical. The patch creates a single function that either counts the number of tasks waiting for zero or waiting due to a decrease operation. Compared to the initial version, the BUG_ONs were removed. Signed-off-by:
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Manfred Spraul authored
GETZCNT is supposed to return the number of threads that wait until a semaphore value becomes 0. The current implementation overlooks complex operations that contain both wait-for-zero operation and operations that alter at least one semaphore. The patch fixes that. It's intentionally copy&paste, this will be cleaned up in the next patch. Signed-off-by:
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Davidlohr Bueso authored
The need for volatile is not obvious, document it. Signed-off-by:
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Davidlohr Bueso authored
Nothing big and no logical changes, just get rid of some redundant function declarations. Move msg_[init/exit]_ns down the end of the file. Signed-off-by:
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Davidlohr Bueso authored
Call __set_current_state() instead of assigning the new state directly. Signed-off-by:
Manfred Spraul <manfred@colorfullif.com> Cc: Aswin Chandramouleeswaran <aswin@hp.com> Signed-off-by:
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Davidlohr Bueso authored
This is useful in the future and allows users to better understand the reasoning behind the changes. Also use UL as we're dealing with it anyways. Signed-off-by:
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Manfred Spraul authored
System V shared memory a) can be abused to trigger out-of-memory conditions and the standard measures against out-of-memory do not work: - it is not possible to use setrlimit to limit the size of shm segments. - segments can exist without association with any processes, thus the oom-killer is unable to free that memory. b) is typically used for shared information - today often multiple GB. (e.g. database shared buffers) The current default is a maximum segment size of 32 MB and a maximum total size of 8 GB. This is often too much for a) and not enough for b), which means that lots of users must change the defaults. This patch increases the default limits (nearly) to the maximum, which is perfect for case b). The defaults are used after boot and as the initial value for each new namespace. Admins/distros that need a protection against a) should reduce the limits and/or enable shm_rmid_forced. Unix has historically required setting these limits for shared memory, and Linux inherited such behavior. The consequence of this is added complexity for users and administrators. One very common example are Database setup/installation documents and scripts, where users must manually calculate the values for these limits. This also requires (some) knowledge of how the underlying memory management works, thus causing, in many occasions, the limits to just be flat out wrong. Disabling these limits sooner could have saved companies a lot of time, headaches and money for support. But it's never too late, simplify users life now. Further notes: - The patch only changes default, overrides behave as before: # sysctl kernel.shmall=33554432 would recreate the previous limit for SHMMAX (for the current namespace). - Disabling sysv shm allocation is possible with: # sysctl kernel.shmall=0 (not a new feature, also per-namespace) - The limits are intentionally set to a value slightly less than ULONG_MAX, to avoid triggering overflows in user space apps. [not unreasonable, see http://marc.info/?l=linux-mm&m=139638334330127] Signed-off-by:Michael Kerrisk <mtk.manpages@gmail.com> Acked-by:
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by:
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Manfred Spraul authored
SHMMAX is the upper limit for the size of a shared memory segment, counted in bytes. The actual allocation is that size, rounded up to the next full page. Add a check that prevents the creation of segments where the rounded up size causes an integer overflow. Signed-off-by:
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Manfred Spraul authored
shm_tot counts the total number of pages used by shm segments. If SHMALL is ULONG_MAX (or nearly ULONG_MAX), then the number can overflow. Subsequent calls to shmctl(,SHM_INFO,) would return wrong values for shm_tot. The patch adds a detection for overflows. Signed-off-by:
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Manfred Spraul authored
The increase of SHMMAX/SHMALL is a 4 patch series. The change itself is trivial, the only problem are interger overflows. The overflows are not new, but if we make huge values the default, then the code should be free from overflows. SHMMAX: - shmmem_file_setup places a hard limit on the segment size: MAX_LFS_FILESIZE. On 32-bit, the limit is > 1 TB, i.e. 4 GB-1 byte segments are possible. Rounded up to full pages the actual allocated size is 0. --> must be fixed, patch 3 - shmat: - find_vma_intersection does not handle overflows properly. --> must be fixed, patch 1 - the rest is fine, do_mmap_pgoff limits mappings to TASK_SIZE and checks for overflows (i.e.: map 2 GB, starting from addr=2.5GB fails). SHMALL: - after creating 8192 segments size (1L<<63)-1, shm_tot overflows and returns 0. --> must be fixed, patch 2. Userspace: - Obviously, there could be overflows in userspace. There is nothing we can do, only use values smaller than ULONG_MAX. I ended with "ULONG_MAX - 1L<<24": - TASK_SIZE cannot be used because it is the size of the current task. Could be 4G if it's a 32-bit task on a 64-bit kernel. - The maximum size is not standardized across archs: I found TASK_MAX_SIZE, TASK_SIZE_MAX and TASK_SIZE_64. - Just in case some arch revives a 4G/4G split, nearly ULONG_MAX is a valid segment size. - Using "0" as a magic value for infinity is even worse, because right now 0 means 0, i.e. fail all allocations. This patch (of 4): find_vma_intersection() does not work as intended if addr+size overflows. The patch adds a manual check before the call to find_vma_intersection. Signed-off-by: -
Paul McQuade authored
trailing whitespace Signed-off-by:
Paul McQuade <paulmcquad@gmail.com> Signed-off-by:
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Paul McQuade authored
Use #include <linux/uaccess.h> instead of <asm/uaccess.h> Use #include <linux/types.h> instead of <asm/types.h> Signed-off-by:
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