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2011-06-19Merge branch 'core-urgent-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: rcu: Move RCU_BOOST #ifdefs to header file rcu: use softirq instead of kthreads except when RCU_BOOST=y rcu: Use softirq to address performance regression rcu: Simplify curing of load woes
2011-06-16Merge branch 'rc-fixes' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6 * 'rc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6: kbuild: Call depmod.sh via shell perf: clear out make flags when calling kernel make kernelver
2011-06-15perf: clear out make flags when calling kernel make kernelverAndy Whitcroft
When generating the perf version from the kernel version using 'make kernelver' it is necessary to clear out any MAKEFLAGS otherwise they may trigger additional output which pollute the contents. Signed-off-by: Andy Whitcroft <apw@canonical.com> Signed-off-by: Michal Marek <mmarek@suse.cz>
2011-06-14rcu: Use softirq to address performance regressionShaohua Li
Commit a26ac2455ffcf3(rcu: move TREE_RCU from softirq to kthread) introduced performance regression. In an AIM7 test, this commit degraded performance by about 40%. The commit runs rcu callbacks in a kthread instead of softirq. We observed high rate of context switch which is caused by this. Out test system has 64 CPUs and HZ is 1000, so we saw more than 64k context switch per second which is caused by RCU's per-CPU kthread. A trace showed that most of the time the RCU per-CPU kthread doesn't actually handle any callbacks, but instead just does a very small amount of work handling grace periods. This means that RCU's per-CPU kthreads are making the scheduler do quite a bit of work in order to allow a very small amount of RCU-related processing to be done. Alex Shi's analysis determined that this slowdown is due to lock contention within the scheduler. Unfortunately, as Peter Zijlstra points out, the scheduler's real-time semantics require global action, which means that this contention is inherent in real-time scheduling. (Yes, perhaps someone will come up with a workaround -- otherwise, -rt is not going to do well on large SMP systems -- but this patch will work around this issue in the meantime. And "the meantime" might well be forever.) This patch therefore re-introduces softirq processing to RCU, but only for core RCU work. RCU callbacks are still executed in kthread context, so that only a small amount of RCU work runs in softirq context in the common case. This should minimize ksoftirqd execution, allowing us to skip boosting of ksoftirqd for CONFIG_RCU_BOOST=y kernels. Signed-off-by: Shaohua Li <shaohua.li@intel.com> Tested-by: "Alex,Shi" <alex.shi@intel.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2011-06-09Merge branch 'rc-fixes' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6 * 'rc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6: perf: Use make kernelversion instead of parsing the Makefile kbuild: Hack for depmod not handling X.Y versions kbuild: Move depmod call to a separate script kbuild: Fix <linux/version.h> for empty SUBLEVEL or PATCHLEVEL kbuild: Fix KERNELVERSION for empty SUBLEVEL or PATCHLEVEL kbuild: silence Nothing to be done for 'all' message
2011-06-09perf: Use make kernelversion instead of parsing the MakefileMichal Marek
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul Mackerras <paulus@samba.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Signed-off-by: Michal Marek <mmarek@suse.cz>
2011-06-03perf python: Fix argument name list of read_on_cpu()Frederic Weisbecker
Mandatory arguments need to be present in the argument name list, as well as optional arguments, otherwise python barfs: # ./python/twatch.py Traceback (most recent call last): File "./python/twatch.py", line 41, in <module> main() File "./python/twatch.py", line 32, in main event = evlist.read_on_cpu(cpu) RuntimeError: more argument specifiers than keyword list entries Hence, add cpu to the name list. Cc: David Ahern <daahern@cisco.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Stephane Eranian <eranian@google.com> Cc: Tom Zanussi <tzanussi@gmail.com> Link: http://lkml.kernel.org/r/1301588863-20210-1-git-send-email-fweisbec@gmail.com Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2011-06-03perf evlist: Don't die if sample_{id_all|type} is invalidArnaldo Carvalho de Melo
Fixes two more cases where the python binding would not load: . Not finding die(), which it shouldn't anyway, not good to just stop the world because some particular perf.data file is invalid, just propagate the error to the caller. . Not finding perf_sample_size: fix it by moving it from event.c to evsel, where it belongs, as most cases are moving to operate on an evsel object.o One of the fixed problems: [root@emilia ~]# python >>> import perf Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: /home/acme/git/build/perf/python/perf.so: undefined symbol: perf_sample_size >>> [root@emilia ~]# Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Link: http://lkml.kernel.org/n/tip-1hkj7b2cvgbfnoizsekjb6c9@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2011-06-03perf python: Use exception to propagate errorsArnaldo Carvalho de Melo
We were using pr_debug to tell the user about not being able to parse a sample where we should really use the python way of reporting errors: exceptions. Fixes this problem: [root@emilia ~]# python >>> import perf Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: /home/acme/git/build/perf/python/perf.so: undefined symbol: eprintf >>> [root@emilia ~] As we want to keep the objects linked in the python binding (and in the future in a shared library) minimal. Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Link: http://lkml.kernel.org/n/tip-m9dba9kaluas0kq8r58z191c@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2011-06-03perf evlist: Remove dependency on debug routinesArnaldo Carvalho de Melo
So far we avoided having to link debug.o in the python binding, keep it that way by not using ui__warning() in evlist.c. Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Link: http://lkml.kernel.org/n/tip-4wtew8hd3g7ejnlehtspys2t@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2011-05-27perf events: initialize fd array to -1 instead of 0David Ahern
perf_evsel__alloc_fd allocates an array of file descriptors with the memory initialized to 0. The array has dimensions for cpus and threads. Later, __perf_evsel__open calls sys_perf_event_open for each cpu and thread dimensions. If the open fails for any of the cpus or threads then the fd's for this event are closed and the fd entry in the array is set to -1. Now, if the first attempt fails for the event (e.g., the event is not supported) the remaining dimensions (cpu > 0 and thread > 0) are not touched and left at the initialized value of 0. builtin-stat catches ENOENT and ENOSYS failures and allows the command to continue. The end result is that stat attempts to read from an fd of 0 which of course is stdin and so the command hangs until you type ctrl-D. Resolve by initializing the array to -1 since an fd < 0 is already handled. Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1306511914-8016-1-git-send-email-dsahern@gmail.com Signed-off-by: David Ahern <dsahern@gmail.com> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2011-05-26perf tools: Fix build on older systemsArnaldo Carvalho de Melo
Where /usr/include/linux/const.h is not present, e.g. RHEL5. Reported-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Tom Zanussi <tzanussi@gmail.com> Link: http://lkml.kernel.org/n/tip-ypcw2mu0w7dl1rrc6ncz3pee@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2011-05-26perf symbols: Handle /proc/sys/kernel/kptr_restrictArnaldo Carvalho de Melo
Perf uses /proc/modules to figure out where kernel modules are loaded. With the advent of kptr_restrict, non root users get zeroes for all module start addresses. So check if kptr_restrict is non zero and don't generate the syntethic PERF_RECORD_MMAP events for them. Warn the user about it in perf record and in perf report. In perf report the reference relocation symbol being zero means that kptr_restrict was set, thus /proc/kallsyms has only zeroed addresses, so don't use it to fixup symbol addresses when using a valid kallsyms (in the buildid cache) or vmlinux (in the vmlinux path) build-id located automatically or specified by the user. Provide an explanation about it in 'perf report' if kernel samples were taken, checking if a suitable vmlinux or kallsyms was found/specified. Restricted /proc/kallsyms don't go to the buildid cache anymore. Example: [acme@emilia ~]$ perf record -F 100000 sleep 1 WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted, check /proc/sys/kernel/kptr_restrict. Samples in kernel functions may not be resolved if a suitable vmlinux file is not found in the buildid cache or in the vmlinux path. Samples in kernel modules won't be resolved at all. If some relocation was applied (e.g. kexec) symbols may be misresolved even with a suitable vmlinux or kallsyms file. [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.005 MB perf.data (~231 samples) ] [acme@emilia ~]$ [acme@emilia ~]$ perf report --stdio Kernel address maps (/proc/{kallsyms,modules}) were restricted, check /proc/sys/kernel/kptr_restrict before running 'perf record'. If some relocation was applied (e.g. kexec) symbols may be misresolved. Samples in kernel modules can't be resolved as well. # Events: 13 cycles # # Overhead Command Shared Object Symbol # ........ ....... ................. ..................... # 20.24% sleep [kernel.kallsyms] [k] page_fault 20.04% sleep [kernel.kallsyms] [k] filemap_fault 19.78% sleep [kernel.kallsyms] [k] __lru_cache_add 19.69% sleep ld-2.12.so [.] memcpy 14.71% sleep [kernel.kallsyms] [k] dput 4.70% sleep [kernel.kallsyms] [k] flush_signal_handlers 0.73% sleep [kernel.kallsyms] [k] perf_event_comm 0.11% sleep [kernel.kallsyms] [k] native_write_msr_safe # # (For a higher level overview, try: perf report --sort comm,dso) # [acme@emilia ~]$ This is because it found a suitable vmlinux (build-id checked) in /lib/modules/2.6.39-rc7+/build/vmlinux (use -v in perf report to see the long file name). If we remove that file from the vmlinux path: [root@emilia ~]# mv /lib/modules/2.6.39-rc7+/build/vmlinux \ /lib/modules/2.6.39-rc7+/build/vmlinux.OFF [acme@emilia ~]$ perf report --stdio [kernel.kallsyms] with build id 57298cdbe0131f6871667ec0eaab4804dcf6f562 not found, continuing without symbols Kernel address maps (/proc/{kallsyms,modules}) were restricted, check /proc/sys/kernel/kptr_restrict before running 'perf record'. As no suitable kallsyms nor vmlinux was found, kernel samples can't be resolved. Samples in kernel modules can't be resolved as well. # Events: 13 cycles # # Overhead Command Shared Object Symbol # ........ ....... ................. ...... # 80.31% sleep [kernel.kallsyms] [k] 0xffffffff8103425a 19.69% sleep ld-2.12.so [.] memcpy # # (For a higher level overview, try: perf report --sort comm,dso) # [acme@emilia ~]$ Reported-by: Stephane Eranian <eranian@google.com> Suggested-by: David Miller <davem@davemloft.net> Cc: Dave Jones <davej@redhat.com> Cc: David Miller <davem@davemloft.net> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Kees Cook <kees.cook@canonical.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Pekka Enberg <penberg@cs.helsinki.fi> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Tom Zanussi <tzanussi@gmail.com> Link: http://lkml.kernel.org/n/tip-mt512joaxxbhhp1odop04yit@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2011-05-23Merge branch 'perf-urgent-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: perf tools: Fix sample type size calculation in 32 bits archs profile: Use vzalloc() rather than vmalloc() & memset()
2011-05-24perf tools: Fix sample type size calculation in 32 bits archsFrederic Weisbecker
The shift used here to count the number of bits set in the mask doesn't work above the low part for archs that are not 64 bits. Fix the constant used for the shift. This fixes a 32-bit perf top failure reported by Eric Dumazet: Can't parse sample, err = -14 Can't parse sample, err = -14 ... Reported-and-tested-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Stephane Eranian <eranian@google.com Link: http://lkml.kernel.org/r/1306200686-17317-1-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-05-23Merge branch 'perf-urgent-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: perf tools: Fix sample size bit operations perf tools: Fix ommitted mmap data update on remap watchdog: Change the default timeout and configure nmi watchdog period based on watchdog_thresh watchdog: Disable watchdog when thresh is zero watchdog: Only disable/enable watchdog if neccessary watchdog: Fix rounding bug in get_sample_period() perf tools: Propagate event parse error handling perf tools: Robustify dynamic sample content fetch perf tools: Pre-check sample size before parsing perf tools: Move evlist sample helpers to evlist area perf tools: Remove junk code in mmap size handling perf tools: Check we are able to read the event size on mmap
2011-05-23Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial: (39 commits) b43: fix comment typo reqest -> request Haavard Skinnemoen has left Atmel cris: typo in mach-fs Makefile Kconfig: fix copy/paste-ism for dell-wmi-aio driver doc: timers-howto: fix a typo ("unsgined") perf: Only include annotate.h once in tools/perf/util/ui/browsers/annotate.c md, raid5: Fix spelling error in comment ('Ofcourse' --> 'Of course'). treewide: fix a few typos in comments regulator: change debug statement be consistent with the style of the rest Revert "arm: mach-u300/gpio: Fix mem_region resource size miscalculations" audit: acquire creds selectively to reduce atomic op overhead rtlwifi: don't touch with treewide double semicolon removal treewide: cleanup continuations and remove logging message whitespace ath9k_hw: don't touch with treewide double semicolon removal include/linux/leds-regulator.h: fix syntax in example code tty: fix typo in descripton of tty_termios_encode_baud_rate xtensa: remove obsolete BKL kernel option from defconfig m68k: fix comment typo 'occcured' arch:Kconfig.locks Remove unused config option. treewide: remove extra semicolons ...
2011-05-23perf tools: Fix sample size bit operationsFrederic Weisbecker
What we want is to count the number of bits in the mask, not some other random operation written in the middle of the night. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Stephane Eranian <eranian@google.com> Link: http://lkml.kernel.org/r/1306148788-6179-2-git-send-email-fweisbec@gmail.com [ Fixed perf_event__names[] alignment which was nearby and hurting my eyes ... ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-05-23perf tools: Fix ommitted mmap data update on remapFrederic Weisbecker
Commit eac9eacee16 "perf tools: Check we are able to read the event size on mmap" brought a check to ensure we can read the size of the event before dereferencing it, and do a remap otherwise to move the buffer forward. However that remap was ommitting all the necessary work to update the new page offset, head, and to unmap previous pages, etc... To fix this, gather all the code that fetches the event in a seperate helper which does all the necessary checks about the header/event size and tells us anytime a remap is needed. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Stephane Eranian <eranian@google.com> Link: http://lkml.kernel.org/r/1306148788-6179-3-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-05-22Merge branch 'perf/core' of ↵Ingo Molnar
git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing into perf/urgent Conflicts: tools/perf/builtin-top.c Semantic conflict: util/include/linux/list.h # fix prefetch.h removal fallout Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-05-22perf tools: Propagate event parse error handlingFrederic Weisbecker
Better handle event parsing error by propagating the details in upper layers or by dumping some failure message. So that the user knows he has some crazy events in the batch. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Stephane Eranian <eranian@google.com>
2011-05-22perf tools: Robustify dynamic sample content fetchFrederic Weisbecker
Ensure the size of the dynamic fields such as callchains or raw events don't overlap the whole event boundaries. This prevents from dereferencing junk if the given size of the callchain goes too eager. Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Stephane Eranian <eranian@google.com>
2011-05-22perf tools: Pre-check sample size before parsingFrederic Weisbecker
Check that the total size of the sample fields having a fixed size do not exceed the one of the whole event. This robustifies the sample parsing. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Stephane Eranian <eranian@google.com>
2011-05-22perf tools: Move evlist sample helpers to evlist areaFrederic Weisbecker
These APIs should belong to evlist.c as they may not be exclusively tied to the headers. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Stephane Eranian <eranian@google.com
2011-05-22perf tools: Remove junk code in mmap size handlingFrederic Weisbecker
size is overriden later and used only then. Those lines are only junk, probably a leftover. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Stephane Eranian <eranian@google.com>
2011-05-22perf tools: Check we are able to read the event size on mmapFrederic Weisbecker
Check we have enough mmaped space to read the current event size from its headers, otherwise we may dereference some hell there. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Stephane Eranian <eranian@google.com>
2011-05-20sanitize <linux/prefetch.h> usageLinus Torvalds
Commit e66eed651fd1 ("list: remove prefetching from regular list iterators") removed the include of prefetch.h from list.h, which uncovered several cases that had apparently relied on that rather obscure header file dependency. So this fixes things up a bit, using grep -L linux/prefetch.h $(git grep -l '[^a-z_]prefetchw*(' -- '*.[ch]') grep -L 'prefetchw*(' $(git grep -l 'linux/prefetch.h' -- '*.[ch]') to guide us in finding files that either need <linux/prefetch.h> inclusion, or have it despite not needing it. There are more of them around (mostly network drivers), but this gets many core ones. Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-05-19Merge branch 'core-rcu-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (78 commits) Revert "rcu: Decrease memory-barrier usage based on semi-formal proof" net,rcu: convert call_rcu(prl_entry_destroy_rcu) to kfree batman,rcu: convert call_rcu(softif_neigh_free_rcu) to kfree_rcu batman,rcu: convert call_rcu(neigh_node_free_rcu) to kfree() batman,rcu: convert call_rcu(gw_node_free_rcu) to kfree_rcu net,rcu: convert call_rcu(kfree_tid_tx) to kfree_rcu() net,rcu: convert call_rcu(xt_osf_finger_free_rcu) to kfree_rcu() net/mac80211,rcu: convert call_rcu(work_free_rcu) to kfree_rcu() net,rcu: convert call_rcu(wq_free_rcu) to kfree_rcu() net,rcu: convert call_rcu(phonet_device_rcu_free) to kfree_rcu() perf,rcu: convert call_rcu(swevent_hlist_release_rcu) to kfree_rcu() perf,rcu: convert call_rcu(free_ctx) to kfree_rcu() net,rcu: convert call_rcu(__nf_ct_ext_free_rcu) to kfree_rcu() net,rcu: convert call_rcu(net_generic_release) to kfree_rcu() net,rcu: convert call_rcu(netlbl_unlhsh_free_addr6) to kfree_rcu() net,rcu: convert call_rcu(netlbl_unlhsh_free_addr4) to kfree_rcu() security,rcu: convert call_rcu(sel_netif_free) to kfree_rcu() net,rcu: convert call_rcu(xps_dev_maps_release) to kfree_rcu() net,rcu: convert call_rcu(xps_map_release) to kfree_rcu() net,rcu: convert call_rcu(rps_map_release) to kfree_rcu() ...
2011-05-19Merge branch 'perf-core-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (107 commits) perf stat: Add more cache-miss percentage printouts perf stat: Add -d -d and -d -d -d options to show more CPU events ftrace/kbuild: Add recordmcount files to force full build ftrace: Add self-tests for multiple function trace users ftrace: Modify ftrace_set_filter/notrace to take ops ftrace: Allow dynamically allocated function tracers ftrace: Implement separate user function filtering ftrace: Free hash with call_rcu_sched() ftrace: Have global_ops store the functions that are to be traced ftrace: Add ops parameter to ftrace_startup/shutdown functions ftrace: Add enabled_functions file ftrace: Use counters to enable functions to trace ftrace: Separate hash allocation and assignment ftrace: Create a global_ops to hold the filter and notrace hashes ftrace: Use hash instead for FTRACE_FL_FILTER ftrace: Replace FTRACE_FL_NOTRACE flag with a hash of ignored functions perf bench, x86: Add alternatives-asm.h wrapper x86, 64-bit: Fix copy_[to/from]_user() checks for the userspace address limit x86, mem: memset_64.S: Optimize memset by enhanced REP MOVSB/STOSB x86, mem: memmove_64.S: Optimize memmove by enhanced REP MOVSB/STOSB ...
2011-05-18perf bench, x86: Add alternatives-asm.h wrapperIngo Molnar
perf bench needs this to build the kernel's memcpy routine: In file included from bench/mem-memcpy-x86-64-asm.S:2:0: bench/../../../arch/x86/lib/memcpy_64.S:7:33: fatal error: asm/alternative-asm.h: No such file or directory Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/n/tip-c5d41xibgullk8h2280q4gv0@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-05-17perf: Fix multi-event parsing bugStephane Eranian
This patch fixes an issue with event parsing. The following commit appears to have broken the ability to specify a comma separated list of events: commit ceb53fbf6dbb1df26d38379a262c6981fe73dd36 Author: Ingo Molnar <mingo@elte.hu> Date: Wed Apr 27 04:06:33 2011 +0200 perf stat: Fail more clearly when an invalid modifier is specified This patch fixes this while preserving the desired effect: $ perf stat -e instructions:u,instructions:k ls /dev/null /dev/null Performance counter stats for 'ls /dev/null': 365956 instructions:u # 0.00 insns per cycle 731806 instructions:k # 0.00 insns per cycle 0.001108862 seconds time elapsed $ perf stat -e task-clock-msecs true invalid event modifier: '-msecs' Run 'perf list' for a list of valid events and modifiers Signed-off-by: Stephane Eranian <eranian@google.com> Cc: acme@redhat.com Cc: peterz@infradead.org Cc: fweisbec@gmail.com Link: http://lkml.kernel.org/r/20110517133619.GA6999@quad Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-05-15perf evlist: Fix per thread mmap setupArnaldo Carvalho de Melo
The PERF_EVENT_IOC_SET_OUTPUT ioctl was returning -EINVAL when using --pid when monitoring multithreaded apps, as we can only share a ring buffer for events on the same thread if not doing per cpu. Fix it by using per thread ring buffers. Tested with: [root@felicio ~]# tuna -t 26131 -CP | nl 1 thread ctxt_switches 2 pid SCHED_ rtpri affinity voluntary nonvoluntary cmd 3 26131 OTHER 0 0,1 10814276 2397830 chromium-browse 4 642 OTHER 0 0,1 14688 0 chromium-browse 5 26148 OTHER 0 0,1 713602 115479 chromium-browse 6 26149 OTHER 0 0,1 801958 2262 chromium-browse 7 26150 OTHER 0 0,1 1271128 248 chromium-browse 8 26151 OTHER 0 0,1 3 0 chromium-browse 9 27049 OTHER 0 0,1 36796 9 chromium-browse 10 618 OTHER 0 0,1 14711 0 chromium-browse 11 661 OTHER 0 0,1 14593 0 chromium-browse 12 29048 OTHER 0 0,1 28125 0 chromium-browse 13 26143 OTHER 0 0,1 2202789 781 chromium-browse [root@felicio ~]# So 11 threads under pid 26131, then: [root@felicio ~]# perf record -F 50000 --pid 26131 [root@felicio ~]# grep perf_event /proc/`pidof perf`/maps | nl 1 7fa4a2538000-7fa4a25b9000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] 2 7fa4a25b9000-7fa4a263a000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] 3 7fa4a263a000-7fa4a26bb000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] 4 7fa4a26bb000-7fa4a273c000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] 5 7fa4a273c000-7fa4a27bd000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] 6 7fa4a27bd000-7fa4a283e000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] 7 7fa4a283e000-7fa4a28bf000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] 8 7fa4a28bf000-7fa4a2940000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] 9 7fa4a2940000-7fa4a29c1000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] 10 7fa4a29c1000-7fa4a2a42000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] 11 7fa4a2a42000-7fa4a2ac3000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] [root@felicio ~]# 11 mmaps, one per thread since we didn't specify any CPU list, so we need one mmap per thread and: [root@felicio ~]# perf record -F 50000 --pid 26131 ^M ^C[ perf record: Woken up 79 times to write data ] [ perf record: Captured and wrote 20.614 MB perf.data (~900639 samples) ] [root@felicio ~]# perf report -D | grep PERF_RECORD_SAMPLE | cut -d/ -f2 | cut -d: -f1 | sort -n | uniq -c | sort -nr | nl 1 371310 26131 2 96516 26148 3 95694 26149 4 95203 26150 5 7291 26143 6 87 27049 7 76 661 8 60 29048 9 47 618 10 43 642 [root@felicio ~]# Ok, one of the threads, 26151 was quiescent, so no samples there, but all the others are there. Then, if I specify one CPU: [root@felicio ~]# perf record -F 50000 --pid 26131 --cpu 1 ^C[ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.680 MB perf.data (~29730 samples) ] [root@felicio ~]# perf report -D | grep PERF_RECORD_SAMPLE | cut -d/ -f2 | cut -d: -f1 | sort -n | uniq -c | sort -nr | nl 1 8444 26131 2 2584 26149 3 2518 26148 4 2324 26150 5 123 26143 6 9 661 7 9 29048 [root@felicio ~]# This machine has two cores, so fewer threads appeared on the radar, and: [root@felicio ~]# grep perf_event /proc/`pidof perf`/maps | nl 1 7f484b922000-7f484b9a3000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] [root@felicio ~]# Just one mmap, as now we can use just one per-cpu buffer instead of the per-thread needed in the previous case. For global profiling: [root@felicio ~]# perf record -F 50000 -a ^C[ perf record: Woken up 26 times to write data ] [ perf record: Captured and wrote 7.128 MB perf.data (~311412 samples) ] [root@felicio ~]# grep perf_event /proc/`pidof perf`/maps | nl 1 7fb49b435000-7fb49b4b6000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] 2 7fb49b4b6000-7fb49b537000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] [root@felicio ~]# It uses per-cpu buffers. For just one thread: [root@felicio ~]# perf record -F 50000 --tid 26148 ^C[ perf record: Woken up 2 times to write data ] [ perf record: Captured and wrote 0.330 MB perf.data (~14426 samples) ] [root@felicio ~]# perf report -D | grep PERF_RECORD_SAMPLE | cut -d/ -f2 | cut -d: -f1 | sort -n | uniq -c | sort -nr | nl 1 9969 26148 [root@felicio ~]# [root@felicio ~]# grep perf_event /proc/`pidof perf`/maps | nl 1 7f286a51b000-7f286a59c000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] [root@felicio ~]# Tested-by: David Ahern <dsahern@gmail.com> Tested-by: Lin Ming <ming.m.lin@intel.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Tom Zanussi <tzanussi@gmail.com> Link: http://lkml.kernel.org/r/20110426204401.GB1746@ghostprotocols.net Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2011-05-15perf tools: Honour the cpu list parameter when also monitoring a thread listArnaldo Carvalho de Melo
The perf_evlist__create_maps was discarding the --cpu parameter when a --pid or --tid was specified, fix that. Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Tom Zanussi <tzanussi@gmail.com> Link: http://lkml.kernel.org/r/20110426204401.GB1746@ghostprotocols.net Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2011-05-10perf probe: Fix the missed parameter initializationLin Ming
pubname_callback_param::found should be initialized to 0 in fastpath lookup, the structure is on the stack and uninitialized otherwise. Signed-off-by: Lin Ming <ming.m.lin@intel.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Link: http://lkml.kernel.org/r/1304066518-30420-2-git-send-email-ming.m.lin@intel.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-05-10perf: Only include annotate.h once in tools/perf/util/ui/browsers/annotate.cJesper Juhl
Including "../../annotate.h" once in tools/perf/util/ui/browsers/annotate.c is enough. No need to do it twice. Signed-off-by: Jesper Juhl <jj@chaosbits.net> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2011-05-05rcu: move TREE_RCU from softirq to kthreadPaul E. McKenney
If RCU priority boosting is to be meaningful, callback invocation must be boosted in addition to preempted RCU readers. Otherwise, in presence of CPU real-time threads, the grace period ends, but the callbacks don't get invoked. If the callbacks don't get invoked, the associated memory doesn't get freed, so the system is still subject to OOM. But it is not reasonable to priority-boost RCU_SOFTIRQ, so this commit moves the callback invocations to a kthread, which can be boosted easily. Also add comments and properly synchronized all accesses to rcu_cpu_kthread_task, as suggested by Lai Jiangshan. 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>
2011-04-29perf list: Fix max event string sizeIngo Molnar
Recent stalled-cycles event names were larger than the 40 chars printout used by perf list. Extend that, make it robust for future extensions and also adjust alignments in face of wider event names. Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Link: http://lkml.kernel.org/n/tip-7y40wib8n009io7hjpn1dsrm@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-29perf stat: Analyze front-end and back-end stall countsIngo Molnar
Sample output: Performance counter stats for './loop_1b': 873.691065 task-clock # 1.000 CPUs utilized 1 context-switches # 0.000 M/sec 1 CPU-migrations # 0.000 M/sec 96 page-faults # 0.000 M/sec 2,012,637,222 cycles # 2.304 GHz (66.58%) 1,001,397,911 stalled-cycles-frontend # 49.76% frontend cycles idle (66.58%) 7,523,398 stalled-cycles-backend # 0.37% backend cycles idle (66.76%) 2,004,551,046 instructions # 1.00 insns per cycle # 0.50 stalled cycles per insn (66.80%) 1,001,304,992 branches # 1146.063 M/sec (66.76%) 39,453 branch-misses # 0.00% of all branches (66.64%) 0.874046121 seconds time elapsed Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Link: http://lkml.kernel.org/n/tip-7y40wib8n003io7hjpn1dsrm@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-29perf tools: Add front-end and back-end stalled cycles supportIngo Molnar
Update perf tooling to deal with front-end and back-end stalled cycles events. Add both the default 'perf stat' output. Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Link: http://lkml.kernel.org/n/tip-7y40wib8n002io7hjpn1dsrm@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-26perf stat: Add stalled cycles to the default outputIngo Molnar
The new default output looks like this: Performance counter stats for './loop_1b_instructions': 236.010686 task-clock # 0.996 CPUs utilized 0 context-switches # 0.000 M/sec 0 CPU-migrations # 0.000 M/sec 99 page-faults # 0.000 M/sec 756,487,646 cycles # 3.205 GHz 354,938,996 stalled-cycles # 46.92% of all cycles are idle 1,001,403,797 instructions # 1.32 insns per cycle # 0.35 stalled cycles per insn 100,279,773 branches # 424.895 M/sec 12,646 branch-misses # 0.013 % of all branches 0.236902540 seconds time elapsed We dropped cache-refs and cache-misses and added stalled-cycles - this is a more generic "how well utilized is the CPU" metric. If the stalled-cycles ratio is too high then more specific measurements can be taken to figure out the source of the inefficiency. Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Link: http://lkml.kernel.org/n/tip-pbpl2l4mn797s69bclfpwkwn@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-26perf stat: Make all displayed event names parseable as wellIngo Molnar
Right now we display this by default: 0.202204 task-clock-msecs # 0.282 CPUs 0 context-switches # 0.000 M/sec 0 CPU-migrations # 0.000 M/sec 85 page-faults # 0.420 M/sec The task-clock-msecs event cannot actually be passed back as an event name, the event name we recognize is 'task-clock'. So change the output of the cpu-clock and task-clock events to be idempotent. ( Units should be printed out in the right-side column, if needed. ) Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Link: http://lkml.kernel.org/n/tip-lexrnbzy09asscgd4f7oac4i@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-26perf stat: Fail more clearly when an invalid modifier is specifiedIngo Molnar
Currently we fail without printing any error message on "perf stat -e task-clock-msecs". The reason is that the task-clock event is matched and the "-msecs" postfix is assumed to be an event modifier - but is not recognized. This patch changes the code to be more informative: $ perf stat -e task-clock-msecs true invalid event modifier: '-msecs' Run 'perf list' for a list of valid events and modifiers And restructures the return value of parse_event_modifier() to allow the printing of all variants of invalid event modifiers. Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Link: http://lkml.kernel.org/n/tip-wlaw3dvz1ly6wple8l52cfca@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-26perf tools: Accept case-insensitive symbolic event variantsIngo Molnar
We currently fail on something like '-e CPU-migrations', with: invalid or unsupported event: 'CPU-migrations' While 'CPU-migrations' is how we actually print out the event in the default perf stat output: Performance counter stats for 'true': 0.202204 task-clock-msecs # 0.282 CPUs 0 context-switches # 0.000 M/sec 0 CPU-migrations # 0.000 M/sec So change the matching to be case-insensitive. Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Link: http://lkml.kernel.org/n/tip-omcm3edjjtx83a4kh2e244se@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-26perf events: Add stalled cycles generic event - PERF_COUNT_HW_STALLED_CYCLESIngo Molnar
The new PERF_COUNT_HW_STALLED_CYCLES event tries to approximate cycles the CPU does nothing useful, because it is stalled on a cache-miss or some other condition. Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Link: http://lkml.kernel.org/n/tip-fue11vymwqsoo5to72jxxjyl@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-20perf script: improve validation of sample attributes for output fieldsDavid Ahern
Check for required sample attributes using evsel rather than sample_type in the session header. If the attribute for a default field is not present for the event type (e.g., new command operating on file from older kernel) the field is removed from the output list. Expected event types must exist. For example, if a user specifies -f trace:time,trace -f sw:time,cpu,sym the perf.data file must contain both tracepoints and software events (ie., it is an error if either does not exist in the file). Attribute checking is done once at the beginning of perf-script rather than for each sample. v1 -> v2: - addressed comments from acme Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1302148460-570-1-git-send-email-daahern@cisco.com Signed-off-by: David Ahern <daahern@cisco.com> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2011-04-19perf symbols: Give more useful names to 'self' parametersArnaldo Carvalho de Melo
One more installment on an area that is mostly dormant. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tom Zanussi <tzanussi@gmail.com> LKML-Reference: <new-submission> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2011-04-19Merge branch 'perf/urgent' into perf/coreIngo Molnar
Merge reason: we'll be queueing up dependent changes. Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-15perf evsel: Fix use of inheritArnaldo Carvalho de Melo
perf stat doesn't mmap and its perfectly fine for it to use task-bound counters with inheritance. So set the attr.inherit on the caller and leave the syscall itself to validate it. When the mmap fails perf_evlist__mmap will just emit a warning if this is the failure reason. Reported-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Tom Zanussi <tzanussi@gmail.com> Link: http://lkml.kernel.org/r/20110414170121.GC3229@ghostprotocols.net Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2011-04-15perf hists browser: Fix seg fault when annotate null symbolLin Ming
In hists browser, press hotkey 'a' to annotate current symbol. Now it causes segment fault if 'a' is pressed on a null symbol. Here are 2 small bugs: - In perf_evsel__hists_browse, the condition check after 'a' is pressed is not correct, we should check ->sym instead of ->map. - In symbol__tui_annotate we must check whether sym is NULL or not before getting annotation structure. This patch fixes above 2 small bugs. Link: http://lkml.kernel.org/r/1302244286.4106.36.camel@minggr.sh.intel.com Signed-off-by: Lin Ming <ming.m.lin@intel.com> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2011-04-08perf: Fix a build error with some GCC versionsEric Dumazet
Fix this: util/cgroup.c: In function ‘open_cgroup’: util/cgroup.c:16:16: error: ‘saved_ptr’ may be used uninitialized in this function util/cgroup.c:16:16: note: ‘saved_ptr’ was declared here Apparently newer GCC (4.6) can figure out that this variable is properly initialized - but some versions of GCC (such as 4.5.2) need help. Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>