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2012-07-06rcu: Fix code-style issues involving "else"Paul E. McKenney
The Linux kernel coding style says that single-statement blocks should omit curly braces unless the other leg of the "if" statement has multiple statements, in which case the curly braces should be included. This commit fixes RCU's violations of this rule. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-06Merge branches 'bigrtm.2012.07.04a', 'doctorture.2012.07.02a', ↵Paul E. McKenney
'fixes.2012.07.06a' and 'fnh.2012.07.02a' into HEAD bigrtm: First steps towards getting RCU out of the way of tens-of-microseconds real-time response on systems compiled with NR_CPUS=4096. Also cleanups for and increased concurrency of rcu_barrier() family of primitives. doctorture: rcutorture and documentation improvements. fixes: Miscellaneous fixes. fnh: RCU_FAST_NO_HZ fixes and improvements.
2012-07-06rcu: Introduce check for callback list/count mismatchPaul E. McKenney
The recent bug that introduced the RCU callback list/count mismatch showed the need for a diagnostic to check for this, which this commit adds. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Make RCU_FAST_NO_HZ respect nohz= boot parameterPaul E. McKenney
If the nohz= boot parameter disables nohz, then RCU_FAST_NO_HZ needs to also disable itself. This commit therefore checks for tick_nohz_enabled being zero, disabling rcu_prepare_for_idle() if so. This commit assumes that tick_nohz_enabled can change at runtime: If this is not the case, then a simpler approach suffices. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02rcu: Round FAST_NO_HZ lazy timeout to nearest secondPaul E. McKenney
Currently, if several CPUs in the same package have all lazy RCU callbacks, their wakeups will be uncorrelated. If all the CPUs are in the same power domain (as is often the case), this will result in unnecessary power-ups of the package. This commit therefore uses round_jiffies() to round the timeouts to a second boundary, increasing the odds that they can be coalesced with each other or with other timeouts. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02rcu: The rcu_needs_cpu() function is not a quiescent statePaul E. McKenney
The TINY_PREEMPT_RCU() function rcu_preempt_needs_cpu(), which is called from rcu_needs_cpu(), assumes that it is in a quiescent state with respect to the CPU. This is no longer the case. This commit therefore updates rcu_preempt_needs_cpu() to make it aware that it is not running in a quiescent state. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com> Tested-by: Pascal Chapperon <pascal.chapperon@wanadoo.fr>
2012-07-02rcu: Dump only the current CPU's buffers for idle-entry/exit warningsPaul E. McKenney
Problems in RCU idle entry and exit are almost always confined to the offending CPU. This commit therefore switches ftrace_dump() from DUMP_ALL to DUMP_ORIG. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com> Tested-by: Pascal Chapperon <pascal.chapperon@wanadoo.fr>
2012-07-02rcu: Add check for CPUs going offline with callbacks queuedPaul E. McKenney
If a CPU goes offline with callbacks queued, those callbacks might be indefinitely postponed, which can result in a system hang. This commit therefore inserts warnings for this condition. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02rcu: Disable preemption in rcu_blocking_is_gp()Paul E. McKenney
It is time to optimize CONFIG_TREE_PREEMPT_RCU's synchronize_rcu() for uniprocessor optimization, which means that rcu_blocking_is_gp() can no longer rely on RCU read-side critical sections having disabled preemption. This commit therefore disables preemption across rcu_blocking_is_gp()'s scan of the cpu_online_mask. (Updated from previous version to fix embarrassing bug spotted by Wu Fengguang.) Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02rcu: Prevent uninitialized string in RCU CPU stall infoCarsten Emde
An uninitialized string may be displayed at the end of the rcu_preempt detected stall info such as 0: (1 GPs behind) idle=075/140000000000000/0 =8?^D=8?^D ^^^^^^^^^^ if CONFIG_RCU_FAST_NO_HZ is not defined. This trivial patch clears the string in this case. Signed-off-by: Carsten Emde <C.Emde@osadl.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02rcu: Fix rcu_is_cpu_idle() #ifdef in TINY_RCUPaul E. McKenney
The rcu_is_cpu_idle() function is used if CONFIG_DEBUG_LOCK_ALLOC, but TINY_RCU defines it only when CONFIG_PROVE_RCU. This causes build failures when CONFIG_DEBUG_LOCK_ALLOC=y but CONFIG_PROVE_RCU=n. This commit therefore adjusts the #ifdefs for rcu_is_cpu_idle() so that it is defined when CONFIG_DEBUG_LOCK_ALLOC=y. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02rcu: Split RCU core processing out of __call_rcu()Paul E. McKenney
The __call_rcu() function is a bit overweight, so this commit splits it into actual enqueuing of and accounting for the callback (__call_rcu()) and associated RCU-core processing (__call_rcu_core()). Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Prevent __call_rcu() from invoking RCU core on offline CPUsPaul E. McKenney
The __call_rcu() function will invoke the RCU core, for example, if it detects that the current CPU has too many callbacks. However, this can happen on an offline CPU that is on its way to the idle loop, in which case it is an error to invoke the RCU core, and the excess callbacks will be adopted in any case. This commit therefore adds checks to __call_rcu() for running on an offline CPU, refraining from invoking the RCU core in this case. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Make __call_rcu() handle invocation from idlePaul E. McKenney
Although __call_rcu() is handled correctly when called from a momentary non-idle period, if it is called on a CPU that RCU believes to be idle on RCU_FAST_NO_HZ kernels, the callback might be indefinitely postponed. This commit therefore ensures that RCU is aware of the new callback and has a chance to force the CPU out of dyntick-idle mode when a new callback is posted. Reported-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Consolidate tree/tiny __rcu_read_{,un}lock() implementationsPaul E. McKenney
The CONFIG_TREE_PREEMPT_RCU and CONFIG_TINY_PREEMPT_RCU versions of __rcu_read_lock() and __rcu_read_unlock() are identical, so this commit consolidates them into kernel/rcupdate.h. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Add ACCESS_ONCE() to ->qlen accessesPaul E. McKenney
The _rcu_barrier() function accesses other CPUs' rcu_data structure's ->qlen field without benefit of locking. This commit therefore adds the required ACCESS_ONCE() wrappers around accesses and updates that need it. ACCESS_ONCE() is not needed when a CPU accesses its own ->qlen, or in code that cannot run while _rcu_barrier() is sampling ->qlen fields. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Consolidate duplicate callback-list initializationPaul E. McKenney
There are a couple of open-coded initializations of the rcu_data structure's RCU callback list. This commit therefore consolidates them into a new init_callback_list() function. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Fix detection of abruptly-ending stallPaul E. McKenney
The code that attempts to identify stalls that end just as we detect them is broken by both flavors of initialization failure. This commit therefore properly initializes and computes the count of the number of reasons why the RCU grace period is stalled. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Make rcutorture fakewriters invoke rcu_barrier()Paul E. McKenney
The current rcutorture rcu_barrier() testing never intentionally runs more than one instance of rcu_barrier() at a given time. This fails to test the the shiny new concurrency features of rcu_barrier(). This commit therefore modifies the rcutorture fakewriter kthread to randomly invoke rcu_barrier() rather than the usual synchronize_rcu(). Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02rcu: Fix diagnostic-printk typo in rcutorturePaul E. McKenney
The rcu_torture_barrier() function has a copy-and-paste typo in the string passed to rcutorture_shutdown_absorb(), which this commit fixes. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Fix bug in rcu_barrier() torture testPaul E. McKenney
The child threads in the rcu_torture_barrier_cbs() are improperly synchronized, which can cause the rcu_barrier() tests to hang. The failure mode is as follows: 1. CPU 0 running in rcu_torture_barrier() sets barrier_cbs_count to n_barrier_cbs. 2. CPU 1 running in rcu_torture_barrier_cbs() wakes up, posts its RCU callback, and atomically decrements barrier_cbs_count. Because barrier_cbs_count is not zero, it does not do the wake_up(). 3. CPU 2 running in rcu_torture_barrier_cbs() wakes up, but finds that barrier_cbs_count is not equal to n_barrier_cbs, and so returns to sleep. 4. The value of barrier_cbs_count therefore never reaches zero, which causes the test to hang. This commit therefore uses a phase variable to coordinate the test, preventing this scenario from occurring. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02rcu: Test srcu_barrier() from rcutorture test suitePaul E. McKenney
SRCU now has a call_srcu() and an srcu_barrier(), but rcutorture does not test them. This commit adds the machinery to allow rcutorture's existing tests for call_rcu() and rcu_barrier() to apply to the SRCU equivalents. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Rationalize ordering of torture_ops listPaul E. McKenney
Move the raw SRCU interfaces out of the middle of the normal SRCU interfaces. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: RCU_SAVE_DYNTICK code no longer ever deadPaul E. McKenney
Before RCU had unified idle, the RCU_SAVE_DYNTICK leg of the switch statement in force_quiescent_state() was dead code for CONFIG_NO_HZ=n kernel builds. With unified idle, the code is never dead. This commit therefore removes the "if" statement designed to make gcc aware of when the code was and was not dead. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Use for_each_rcu_flavor() in TREE_RCU tracingPaul E. McKenney
This commit applies the new for_each_rcu_flavor() macro to the kernel/rcutree_trace.c file. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02rcu: Introduce for_each_rcu_flavor() and use itPaul E. McKenney
The arrival of TREE_PREEMPT_RCU some years back included some ugly code involving either #ifdef or #ifdef'ed wrapper functions to iterate over all non-SRCU flavors of RCU. This commit therefore introduces a for_each_rcu_flavor() iterator over the rcu_state structures for each flavor of RCU to clean up a bit of the ugliness. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02rcu: Remove unneeded __rcu_process_callbacks() argumentPaul E. McKenney
With the advent of __this_cpu_ptr(), it is no longer necessary to pass both the rcu_state and rcu_data structures into __rcu_process_callbacks(). This commit therefore computes the rcu_data pointer from the rcu_state pointer within __rcu_process_callbacks() so that callers can pass in only the pointer to the rcu_state structure. This paves the way for linking the rcu_state structures together and iterating over them. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Add rcu_barrier() statistics to debugfs tracingPaul E. McKenney
This commit adds an rcubarrier file to RCU's debugfs statistical tracing directory, providing diagnostic information on rcu_barrier(). Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Add tracing for _rcu_barrier()Paul E. McKenney
This commit adds event tracing for _rcu_barrier() execution. This is defined only if RCU_TRACE=y. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Increase rcu_barrier() concurrencyPaul E. McKenney
The traditional rcu_barrier() implementation has serialized all requests, regardless of RCU flavor, and also does not coalesce concurrent requests. In the past, this has been good and sufficient. However, systems are getting larger and use of rcu_barrier() has been increasing. This commit therefore introduces a counter-based scheme that allows _rcu_barrier() calls for the same flavor of RCU to take advantage of each others' work. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02rcu: Remove needless initializationPaul E. McKenney
For global variables, C defaults all fields to zero. The initialization of the rcu_state structure's ->n_force_qs and ->n_force_qs_ngp fields is therefore redundant, so this commit removes these initializations. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02rcu: Move rcu_barrier_mutex to rcu_state structurePaul E. McKenney
In order to allow each RCU flavor to concurrently execute its rcu_barrier() function, it is necessary to move the relevant state to the rcu_state structure. This commit therefore moves the rcu_barrier_mutex global variable to a new ->barrier_mutex field in the rcu_state structure. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02rcu: Move rcu_barrier_completion to rcu_state structurePaul E. McKenney
In order to allow each RCU flavor to concurrently execute its rcu_barrier() function, it is necessary to move the relevant state to the rcu_state structure. This commit therefore moves the rcu_barrier_completion global variable to a new ->barrier_completion field in the rcu_state structure. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Move rcu_barrier_cpu_count to rcu_state structurePaul E. McKenney
In order to allow each RCU flavor to concurrently execute its rcu_barrier() function, it is necessary to move the relevant state to the rcu_state structure. This commit therefore moves the rcu_barrier_cpu_count global variable to a new ->barrier_cpu_count field in the rcu_state structure. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Move _rcu_barrier()'s rcu_head structures to rcu_data structuresPaul E. McKenney
In order for multiple flavors of RCU to each concurrently run one rcu_barrier(), each flavor needs its own per-CPU set of rcu_head structures. This commit therefore moves _rcu_barrier()'s set of per-CPU rcu_head structures from per-CPU variables to the existing per-CPU and per-RCU-flavor rcu_data structures. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Place pointer to call_rcu() in rcu_data structurePaul E. McKenney
This is a preparatory commit for increasing rcu_barrier()'s concurrency. It adds a pointer in the rcu_data structure to the corresponding call_rcu() function. This allows a pointer to the rcu_data structure to imply the function pointer, which allows _rcu_barrier() state to be placed in the rcu_state structure. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Prevent excessive line length in RCU_STATE_INITIALIZER()Paul E. McKenney
Upcoming rcu_barrier() concurrency commits will result in line lengths greater than 80 characters in the RCU_STATE_INITIALIZER(), so this commit shortens the name of the macro's argument to prevent this. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-07-02rcu: Size rcu_node tree from nr_cpu_ids rather than NR_CPUSPaul E. McKenney
The rcu_node tree array is sized based on compile-time constants, including NR_CPUS. Although this approach has worked well in the past, the recent trend by many distros to define NR_CPUS=4096 results in excessive grace-period-initialization latencies. This commit therefore substitutes the run-time computed nr_cpu_ids for the compile-time NR_CPUS when building the tree. This can result in much of the compile-time-allocated rcu_node array being unused. If this is a major problem, you are in a specialized situation anyway, so you can manually adjust the NR_CPUS, RCU_FANOUT, and RCU_FANOUT_LEAF kernel config parameters. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02rcu: Four-level hierarchy is no longer experimentalPaul E. McKenney
Time to make the four-level-hierarchy setting less scary, so this commit removes "Experimental" from the boot-time message. Leave the message in order to get a heads-up on any possible need to expand to a five-level hierarchy. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02rcu: Control RCU_FANOUT_LEAF from boot-time parameterPaul E. McKenney
Although making RCU_FANOUT_LEAF a kernel configuration parameter rather than a fixed constant makes it easier for people to decrease cache-miss overhead for large systems, it is of little help for people who must run a single pre-built kernel binary. This commit therefore allows the value of RCU_FANOUT_LEAF to be increased (but not decreased!) via a boot-time parameter named rcutree.rcu_fanout_leaf. Reported-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-07-02Revert "rcu: Move PREEMPT_RCU preemption to switch_to() invocation"Paul E. McKenney
This reverts commit 616c310e83b872024271c915c1b9ab505b9efad9. (Move PREEMPT_RCU preemption to switch_to() invocation). Testing by Sasha Levin <levinsasha928@gmail.com> showed that this can result in deadlock due to invoking the scheduler when one of the runqueue locks is held. Because this commit was simply a performance optimization, revert it. Reported-by: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Sasha Levin <levinsasha928@gmail.com>
2012-06-30printk.c: fix kernel-doc warningsRandy Dunlap
Fix kernel-doc warnings in printk.c: use correct parameter name. Warning(kernel/printk.c:2429): No description found for parameter 'buf' Warning(kernel/printk.c:2429): Excess function parameter 'line' description in 'kmsg_dump_get_buffer' Signed-off-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-06-30Merge tag 'driver-core-3.5-rc5' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core Pull driver Core fixes from Greg Kroah-Hartman: "Here is a number of printk() fixes, specifically a few reported by the crazy blog program that ships in SUSE releases (that's "boot log" and not "web log", it predates the general "blog" terminology by many years), and the restoration of the continuation line functionality reported by Stephen and others. Yes, the changes seem a bit big this late in the cycle, but I've been beating on them for a while now, and Stephen has even optimized it a bit, so all looks good to me. The other change in here is a Documentation update for the stable kernel rules describing how some distro patches should be backported, to hopefully drive a bit more response from the distros to the stable kernel releases. Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>" * tag 'driver-core-3.5-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: printk: Optimize if statement logic where newline exists printk: flush continuation lines immediately to console syslog: fill buffer with more than a single message for SYSLOG_ACTION_READ Revert "printk: return -EINVAL if the message len is bigger than the buf size" printk: fix regression in SYSLOG_ACTION_CLEAR stable: Allow merging of backports for serious user-visible performance issues
2012-06-29printk: Optimize if statement logic where newline existsSteven Rostedt
In reviewing Kay's fix up patch: "printk: Have printk() never buffer its data", I found two if statements that could be combined and optimized. Put together the two 'cont.len && cont.owner == current' if statements into a single one, and check if we need to call cont_add(). This also removes the unneeded double cont_flush() calls. Link: http://lkml.kernel.org/r/1340869133.876.10.camel@mop Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-29printk: flush continuation lines immediately to consoleKay Sievers
Continuation lines are buffered internally, intended to merge the chunked printk()s into a single record, and to isolate potentially racy continuation users from usual terminated line users. This though, has the effect that partial lines are not printed to the console in the moment they are emitted. In case the kernel crashes in the meantime, the potentially interesting printed information would never reach the consoles. Here we share the continuation buffer with the console copy logic, and partial lines are always immediately flushed to the available consoles. They are still buffered internally to improve the readability and integrity of the messages and minimize the amount of needed record headers to store. Signed-off-by: Kay Sievers <kay@vrfy.org> Tested-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-26syslog: fill buffer with more than a single message for SYSLOG_ACTION_READJan Beulich
The recent changes to the printk buffer management resulted in SYSLOG_ACTION_READ to only return a single message, whereas previously the buffer would get filled as much as possible. As, when too small to fit everything, filling it to the last byte would be pretty ugly with the new code, the patch arranges for as many messages as possible to get returned in a single invocation. User space tools in at least all SLES versions depend on the old behavior. This at once addresses the issue attempted to get fixed with commit b56a39ac263e5b8cafedd551a49c2105e68b98c2 ("printk: return -EINVAL if the message len is bigger than the buf size"), and since that commit widened the possibility for losing a message altogether, the patch here assumes that this other commit would get reverted first (otherwise the patch here won't apply). Furthermore, this patch also addresses the problem dealt with in commit 4a77a5a06ec66ed05199b301e7c25f42f979afdc ("printk: use mutex lock to stop syslog_seq from going wild"), so I'd recommend reverting that one too (albeit there's no direct collision between the two). Signed-off-by: Jan Beulich <jbeulich@suse.com> Acked-by: Kay Sievers <kay@vrfy.org> Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-26Revert "printk: return -EINVAL if the message len is bigger than the buf size"Greg Kroah-Hartman
This reverts commit b56a39ac263e5b8cafedd551a49c2105e68b98c2. A better patch from Jan will follow this to resolve the issue. Acked-by: Kay Sievers <kay@vrfy.org> Cc: Fengguang Wu <wfg@linux.intel.com> Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com> Cc: Jan Beulich <JBeulich@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-25rcu: Stop rcu_do_batch() from multiplexing the "count" variablePaul E. McKenney
Commit b1420f1c (Make rcu_barrier() less disruptive) rearranged the code in rcu_do_batch(), moving the ->qlen manipulation to follow the requeueing of the callbacks. Unfortunately, this rearrangement clobbered the value of the "count" local variable before the value of rdp->qlen was adjusted, resulting in the value of rdp->qlen being inaccurate. This commit therefore introduces an index variable "i", avoiding the inadvertent multiplexing. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-06-25printk: fix regression in SYSLOG_ACTION_CLEARAlan Stern
Commit 7ff9554bb578ba02166071d2d487b7fc7d860d62 (printk: convert byte-buffer to variable-length record buffer) introduced a regression by accidentally removing a "break" statement from inside the big switch in printk's do_syslog(). The symptom of this bug is that the "dmesg -C" command doesn't only clear the kernel's log buffer; it also disables console logging. This patch (as1561) fixes the regression by adding the missing "break". Signed-off-by: Alan Stern <stern@rowland.harvard.edu> CC: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-22Merge branch 'perf-urgent-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull perf updates from Ingo Molnar. * 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: ftrace: Make all inline tags also include notrace perf: Use css_tryget() to avoid propping up css refcount perf tools: Fix synthesizing tracepoint names from the perf.data headers perf stat: Fix default output file perf tools: Fix endianity swapping for adds_features bitmask