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- Jul 19, 2007
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Peter Zijlstra authored
__acquire | lock _____ | \ | __contended | | | wait | _______/ |/ | __acquired | __release | unlock We measure acquisition and contention bouncing. This is done by recording a cpu stamp in each lock instance. Contention bouncing requires the cpu stamp to be set on acquisition. Hence we move __acquired into the generic path. __acquired is then used to measure acquisition bouncing by comparing the current cpu with the old stamp before replacing it. __contended is used to measure contention bouncing (only useful for preemptable locks) [akpm@linux-foundation.org: cleanups] Signed-off-by:Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by:
Ingo Molnar <mingo@elte.hu> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Peter Zijlstra authored
- update the copyright notices - use the default hash function - fix a thinko in a BUILD_BUG_ON - add a WARN_ON to spot inconsitent naming - fix a termination issue in /proc/lock_stat [akpm@linux-foundation.org: cleanups] Signed-off-by:
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Peter Zijlstra authored
Present all this fancy new lock statistics information: *warning, _wide_ output ahead* (output edited for purpose of brevity) # cat /proc/lock_stat lock_stat version 0.1 ----------------------------------------------------------------------------------------------------------------------------------------------------------------- class name contentions waittime-min waittime-max waittime-total acquisitions holdtime-min holdtime-max holdtime-total ----------------------------------------------------------------------------------------------------------------------------------------------------------------- &inode->i_mutex: 14458 6.57 398832.75 2469412.23 6768876 0.34 11398383.65 339410830.89 --------------- &inode->i_mutex 4486 [<ffffffff802a08f9>] pipe_wait+0x86/0x8d &inode->i_mutex 0 [<ffffffff802a01e8>] pipe_write_fasync+0x29/0x5d &inode->i_mutex 0 [<ffffffff802a0e18>] pipe_read+0x74/0x3a5 &inode->i_mutex 0 [<ffffffff802a1a6a>] do_lookup+0x81/0x1ae ................................................................................................................................................................. &inode->i_data.tree_lock-W: 491 0.27 62.47 493.89 2477833 0.39 468.89 1146584.25 &inode->i_data.tree_lock-R: 65 0.44 4.27 48.78 26288792 0.36 184.62 10197458.24 -------------------------- &inode->i_data.tree_lock 46 [<ffffffff80277095>] __do_page_cache_readahead+0x69/0x24f &inode->i_data.tree_lock 31 [<ffffffff8026f9fb>] add_to_page_cache+0x31/0xba &inode->i_data.tree_lock 0 [<ffffffff802770ee>] __do_page_cache_readahead+0xc2/0x24f &inode->i_data.tree_lock 0 [<ffffffff8026f6e4>] find_get_page+0x1a/0x58 ................................................................................................................................................................. proc_inum_idr.lock: 0 0.00 0.00 0.00 36 0.00 65.60 148.26 proc_subdir_lock: 0 0.00 0.00 0.00 3049859 0.00 106.81 1563212.42 shrinker_rwsem-W: 0 0.00 0.00 0.00 5 0.00 1.73 3.68 shrinker_rwsem-R: 0 0.00 0.00 0.00 633 2.57 246.57 10909.76 'contentions' and 'acquisitions' are the number of such events measured (since the last reset). The waittime- and holdtime- (min, max, total) numbers are presented in microseconds. If there are any contention points, the lock class is presented in the block format (as i_mutex and tree_lock above), otherwise a single line of output is presented. The output is sorted on absolute number of contentions (read + write), this should get the worst offenders presented first, so that: # grep : /proc/lock_stat | head will quickly show who's bad. The stats can be reset using: # echo 0 > /proc/lock_stat [bunk@stusta.de: make 2 functions static] [akpm@linux-foundation.org: fix printk warning] Signed-off-by:Jason Baron <jbaron@redhat.com> Signed-off-by:
Adrian Bunk <bunk@stusta.de> Signed-off-by:
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Peter Zijlstra authored
Introduce the core lock statistics code. Lock statistics provides lock wait-time and hold-time (as well as the count of corresponding contention and acquisitions events). Also, the first few call-sites that encounter contention are tracked. Lock wait-time is the time spent waiting on the lock. This provides insight into the locking scheme, that is, a heavily contended lock is indicative of a too coarse locking scheme. Lock hold-time is the duration the lock was held, this provides a reference for the wait-time numbers, so they can be put into perspective. 1) lock 2) ... do stuff .. unlock 3) The time between 1 and 2 is the wait-time. The time between 2 and 3 is the hold-time. The lockdep held-lock tracking code is reused, because it already collects locks into meaningful groups (classes), and because it is an existing infrastructure for lock instrumentation. Currently lockdep tracks lock acquisition with two hooks: lock() lock_acquire() _lock() ... code protected by lock ... unlock() lock_release() _unlock() We need to extend this with two more hooks, in order to measure contention. lock_contended() - used to measure contention events lock_acquired() - completion of the contention These are then placed the following way: lock() lock_acquire() if (!_try_lock()) lock_contended() _lock() lock_acquired() ... do locked stuff ... unlock() lock_release() _unlock() (Note: the try_lock() 'trick' is used to avoid instrumenting all platform dependent lock primitive implementations.) It is also possible to toggle the two lockdep features at runtime using: /proc/sys/kernel/prove_locking /proc/sys/kernel/lock_stat (esp. turning off the O(n^2) prove_locking functionaliy can help) [akpm@linux-foundation.org: build fixes] [akpm@linux-foundation.org: nuke unneeded ifdefs] Signed-off-by: -
Peter Zijlstra authored
Move code around to get fewer but larger #ifdef sections. Break some in-function #ifdefs out into their own functions. Signed-off-by:
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Peter Zijlstra authored
Ensure that all of the lock dependency tracking code is under CONFIG_PROVE_LOCKING. This allows us to use the held lock tracking code for other purposes. Signed-off-by:
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- Jul 17, 2007
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Tejun Heo authored
KSYM_NAME_LEN is peculiar in that it does not include the space for the trailing '\0', forcing all users to use KSYM_NAME_LEN + 1 when allocating buffer. This is nonsense and error-prone. Moreover, when the caller forgets that it's very likely to subtly bite back by corrupting the stack because the last position of the buffer is always cleared to zero. This patch increments KSYM_NAME_LEN by one and updates code accordingly. * off-by-one bug in asm-powerpc/kprobes.h::kprobe_lookup_name() macro is fixed. * Where MODULE_NAME_LEN and KSYM_NAME_LEN were used together, MODULE_NAME_LEN was treated as if it didn't include space for the trailing '\0'. Fix it. Signed-off-by:
Tejun Heo <htejun@gmail.com> Acked-by:
Paulo Marques <pmarques@grupopie.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Signed-off-by:
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- May 08, 2007
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Jarek Poplawski authored
It looks like a remainder from designing... Signed-off-by:
Jarek Poplawski <jarkao@o2.pl> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by:
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Jarek Poplawski authored
Signed-off-by:
Jarek Poplawski <jarkao2@o2.pl> Acked-by:
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Alexey Dobriyan authored
Several kallsyms_lookup() pass dummy arguments but only need, say, module's name. Make kallsyms_lookup() accept NULLs where possible. Also, makes picture clearer about what interfaces are needed for all symbol resolving business. Signed-off-by:
Alexey Dobriyan <adobriyan@sw.ru> Cc: Rusty Russell <rusty@rustcorp.com.au> Acked-by:
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Christoph Hellwig authored
Simplify the stacktrace code: - remove the unused task argument to save_stack_trace, it's always current - remove the all_contexts flag, it's alwasy 0 Signed-off-by:
Christoph Hellwig <hch@lst.de> Cc: Paul Mundt <lethal@linux-sh.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Andi Kleen <ak@suse.de> Cc: Akinobu Mita <akinobu.mita@gmail.com> Acked-by:
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- Mar 22, 2007
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Jarek Poplawski authored
lockdep's data shouldn't be used when debug_locks == 0 because it's not updated after this, so it's more misleading than helpful. PS: probably lockdep's current-> fields should be reset after it turns debug_locks off: so, after printing a bug report, but before return from exported functions, but there are really a lot of these possibilities (e.g. after DEBUG_LOCKS_WARN_ON), so, something could be missed. (Of course direct use of this fields isn't recommended either.) Reported-by:
Folkert van Heusden <folkert@vanheusden.com> Inspired-by:
Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by:
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- Mar 01, 2007
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Sam Ravnborg authored
lockdep_init() is marked __init but used in several places outside __init code. This causes following warnings: $ scripts/mod/modpost kernel/lockdep.o WARNING: kernel/built-in.o - Section mismatch: reference to .init.text:lockdep_init from .text.lockdep_init_map after 'lockdep_init_map' (at offset 0x105) WARNING: kernel/built-in.o - Section mismatch: reference to .init.text:lockdep_init from .text.lockdep_reset_lock after 'lockdep_reset_lock' (at offset 0x35) WARNING: kernel/built-in.o - Section mismatch: reference to .init.text:lockdep_init from .text.__lock_acquire after '__lock_acquire' (at offset 0xb2) The warnings are less obviously due to heavy inlining by gcc - this is not altered. Fix the section mismatch warnings by removing the __init marking, which seems obviously wrong. Signed-off-by:
Sam Ravnborg <sam@ravnborg.org> Acked-by:
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- Feb 20, 2007
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Jarek Poplawski authored
In __lock_acquire check_chain_key can turn off debug_locks, so check is needed to assure proper return code. Signed-off-by:
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- Feb 11, 2007
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Jason Baron authored
Generate locking graph information into /proc/lockdep, for lock hierarchy documentation and visualization purposes. sample output: c089fd5c OPS: 138 FD: 14 BD: 1 --..: &tty->termios_mutex -> [c07a3430] tty_ldisc_lock -> [c07a37f0] &port_lock_key -> [c07afdc0] &rq->rq_lock_key#2 The lock classes listed are all the first-hop lock dependencies that lockdep has seen so far. Signed-off-by:
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Jarek Poplawski authored
- returns after DEBUG_LOCKS_WARN_ON added in 3 places - debug_locks checking after lookup_chain_cache() added in __lock_acquire() - locking for testing and changing global variable max_lockdep_depth added in __lock_acquire() From: Ingo Molnar <mingo@elte.hu> My __acquire_lock() cleanup introduced a locking bug: on SMP systems we'd release a non-owned graph lock. Fix this by moving the graph unlock back, and by leaving the max_lockdep_depth variable update possibly racy. (we dont care, it's just statistics) Also add some minimal debugging code to graph_unlock()/graph_lock(), which caught this locking bug. Signed-off-by:
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- Dec 30, 2006
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Andrew Morton authored
kernel/lockdep.c: In function `lookup_chain_cache': kernel/lockdep.c:1339: warning: long long unsigned int format, u64 arg (arg 2) kernel/lockdep.c:1344: warning: long long unsigned int format, u64 arg (arg 2) Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by:
Andrew Morton <akpm@osdl.org> Signed-off-by:
Linus Torvalds <torvalds@osdl.org>
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- Dec 13, 2006
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Ingo Molnar authored
Jarek Poplawski noticed that lockdep global state could be accessed in a racy way if one CPU did a lockdep assert (shutting lockdep down), while the other CPU would try to do something that changes its global state. This patch fixes those races and cleans up lockdep's internal locking by adding a graph_lock()/graph_unlock()/debug_locks_off_graph_unlock helpers. (Also note that as we all know the Linux kernel is, by definition, bug-free and perfect, so this code never triggers, so these fixes are highly theoretical. I wrote this patch for aesthetic reasons alone.) [akpm@osdl.org: build fix] [jarkao2@o2.pl: build fix's refix] Signed-off-by:
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Ingo Molnar authored
When we print an assert due to scheduling-in-atomic bugs, and if lockdep is enabled, then the IRQ tracing information of lockdep can be printed to pinpoint the code location that disabled interrupts. This saved me quite a bit of debugging time in cases where the backtrace did not identify the irq-disabling site well enough. Signed-off-by:
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Ingo Molnar authored
CONFIG_DEBUG_LOCKDEP is unacceptably slow because it does not utilize the chain-hash. Turn the chain-hash back on in this case too. Signed-off-by:
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Ingo Molnar authored
Cleanup: the VERY_VERBOSE define was unnecessarily dependent on #ifdef VERBOSE - while the VERBOSE switch is 0 or 1 (always defined). Signed-off-by:
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Ingo Molnar authored
Clear all the chains during lockdep_reset(). This fixes some locking-selftest false positives i saw on -rt. (never saw those on mainline though, but it could happen.) Signed-off-by:
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Ingo Molnar authored
Make verbose lockdep messages (off by default) more informative by printing out the hash chain key. (this patch was what helped me catch the earlier lockdep hash-collision bug) Signed-off-by:
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Ingo Molnar authored
Fix typo in the class_filter() function. (filtering is not used by default so this only affects lockdep-internal debugging cases) Signed-off-by:
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- Dec 07, 2006
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Ingo Molnar authored
The hash_lock must only ever be taken with irqs disabled. This happens in all the important places, except one codepath: register_lock_class(). The race should trigger rarely because register_lock_class() is quite rare and single-threaded (happens during init most of the time). The fix is to disable irqs. ( bug found live in -rt: there preemption is alot more agressive and preempting with the hash-lock held caused a lockup.) Signed-off-by:
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Adrian Bunk authored
Remove the no longer used lockdep_internal(). Signed-off-by:
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Jarek Poplawski authored
- numeric string size replaced with constant in print_lock_name and print_lockdep_cache, - return on null pointer in print_lock_dependencies, - one more lockdep return with 0 with unlocking fix in mark_lock. Signed-off-by:
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Jarek Poplawski authored
Here are mainly some lockdep returns with 0 with unlocking fixes. Signed-off-by:
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Peter Zijlstra authored
Stick NFS sockets in their own class to avoid some lockdep warnings. NFS sockets are never exposed to user-space, and will hence not trigger certain code paths that would otherwise pose deadlock scenarios. [akpm@osdl.org: cleanups] Signed-off-by:
Steven Dickson <SteveD@redhat.com> Acked-by:
Neil Brown <neilb@suse.de> Cc: "David S. Miller" <davem@davemloft.net> Signed-off-by:
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- Dec 06, 2006
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Andi Kleen authored
Shouldn't be needed anymore since __kernel_text_address is used unconditionally on x86-64 Signed-off-by:Andi Kleen <ak@suse.de>
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- Nov 17, 2006
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Ingo Molnar authored
lockdep got confused by certain locks in modules: INFO: trying to register non-static key. the code is fine but needs lockdep annotation. turning off the locking correctness validator. Call Trace: [<ffffffff8026f40d>] dump_trace+0xaa/0x3f2 [<ffffffff8026f78f>] show_trace+0x3a/0x60 [<ffffffff8026f9d1>] dump_stack+0x15/0x17 [<ffffffff802abfe8>] __lock_acquire+0x724/0x9bb [<ffffffff802ac52b>] lock_acquire+0x4d/0x67 [<ffffffff80267139>] rt_spin_lock+0x3d/0x41 [<ffffffff8839ed3f>] :ip_conntrack:__ip_ct_refresh_acct+0x131/0x174 [<ffffffff883a1334>] :ip_conntrack:udp_packet+0xbf/0xcf [<ffffffff8839f9af>] :ip_conntrack:ip_conntrack_in+0x394/0x4a7 [<ffffffff8023551f>] nf_iterate+0x41/0x7f [<ffffffff8025946a>] nf_hook_slow+0x64/0xd5 [<ffffffff802369a2>] ip_rcv+0x24e/0x506 [...] Steven Rostedt found the bug: static_obj() check did not take PERCPU_ENOUGH_ROOM into account, so in-module DEFINE_PER_CPU-area locks were triggering this message. Signed-off-by:
Steven Rostedt <srostedt@redhat.com> Signed-off-by:
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- Oct 17, 2006
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Ingo Molnar authored
In general, lockdep warnings are intended to be non-fatal, so I have put in various practical limits on internal data structure failure modes. We haven't had a /single/ lockdep-internal crash ever since lockdep went upstream [the unwinder crashes are outside of lockdep], and that's largely due to the good internal checks it does. Recursion within the dependency graph is currently limited to 20, that's probably not enough on some many-CPU boxes - this patch doubles it to 40. I have written the lockdep functions to have as small stackframes as possible, so 40 should be OK too. (The practical recursion limit should be somewhere between 100 and 200 entries. If we hit that then I'll change the algorithm to be iteration-based. Graph walking logic is so easy to program via recursion, so i'd like to keep recursion as long as possible.) Signed-off-by:
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- Oct 11, 2006
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Alexey Dobriyan authored
Signed-off-by:
Alexey Dobriyan <adobriyan@gmail.com> Acked-by:
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- Oct 10, 2006
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Peter Zijlstra authored
This annotation makes it possible to assign a subclass on lock init. This annotation is meant to reduce the _nested() annotations by assigning a default subclass. One could do without this annotation and rely on lockdep_set_class() exclusively, but that would require a manual stack of struct lock_class_key objects. Signed-off-by:
Dmitry Torokhov <dtor@mail.ru>
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- Oct 02, 2006
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Serge E. Hallyn authored
In some places, particularly drivers and __init code, the init utsns is the appropriate one to use. This patch replaces those with a the init_utsname helper. Changes: Removed several uses of init_utsname(). Hope I picked all the right ones in net/ipv4/ipconfig.c. These are now changed to utsname() (the per-process namespace utsname) in the previous patch (2/7) [akpm@osdl.org: CIFS fix] Signed-off-by:
Serge E. Hallyn <serue@us.ibm.com> Cc: Kirill Korotaev <dev@openvz.org> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Herbert Poetzl <herbert@13thfloor.at> Cc: Andrey Savochkin <saw@sw.ru> Cc: Serge Hallyn <serue@us.ibm.com> Signed-off-by:
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- Sep 29, 2006
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Ingo Molnar authored
With CONFIG_DEBUG_LOCK_ALLOC turned off i was getting sporadic failures in the locking self-test: ------------> | Locking API testsuite: ---------------------------------------------------------------------------- | spin |wlock |rlock |mutex | wsem | rsem | -------------------------------------------------------------------------- A-A deadlock: ok | ok | ok | ok | ok | ok | A-B-B-A deadlock: ok | ok | ok | ok | ok | ok | A-B-B-C-C-A deadlock: ok | ok | ok | ok | ok | ok | A-B-C-A-B-C deadlock: ok | ok | ok | ok | ok | ok | A-B-B-C-C-D-D-A deadlock: ok |FAILED| ok | ok | ok | ok | A-B-C-D-B-D-D-A deadlock: ok | ok | ok | ok | ok | ok | A-B-C-D-B-C-D-A deadlock: ok | ok | ok | ok | ok |FAILED| after much debugging it turned out to be caused by accidental chain-hash key collisions. The current hash is: #define iterate_chain_key(key1, key2) \ (((key1) << MAX_LOCKDEP_KEYS_BITS/2) ^ \ ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS/2)) ^ \ (key2)) where MAX_LOCKDEP_KEYS_BITS is 11. This hash is pretty good as it will shift by 5 bits in every iteration, where every new ID 'mixed' into the hash would have up to 11 bits. But because there was a 6 bits overlap between subsequent IDs and their high bits tended to be similar, there was a chance for accidental chain-hash collision for a low number of locks held. the solution is to shift by 11 bits: #define iterate_chain_key(key1, key2) \ (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \ ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \ (key2)) This keeps the hash perfect up to 5 locks held, but even above that the hash is still good because 11 bits is a relative prime to the total 64 bits, so a complete match will only occur after 64 held locks (which doesnt happen in Linux). Even after 5 locks held, entropy of the 5 IDs mixed into the hash is already good enough so that overlap doesnt generate a colliding hash ID. with this change the false positives went away. Signed-off-by: -
Dave Jones authored
Lets do the same thing we do for oopses - print out the version in the report. It's an extra line of output though. We could tack it on the end of the INFO: lines, but that screws up Ingo's pretty output. Signed-off-by:
Dave Jones <davej@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by:
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- Sep 26, 2006
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Andi Kleen authored
The new dwarf2 unwinder needs to take locks to do backtraces inside modules. This patch makes sure lockdep which calls stacktrace is not reentered. Thanks to Ingo for suggesting this simpler approach. Cc: mingo@elte.hu Signed-off-by: -
Andi Kleen authored
- Remove unused all_contexts parameter No caller used it - Move skip argument into the structure (needed for followon patches) Cc: mingo@elte.hu Signed-off-by:
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- Jul 10, 2006
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Ingo Molnar authored
lockdep_map is embedded into every lock, which blows up data structure sizes all around the kernel. Reduce the class-cache to be for the default class only - that is used in 99.9% of the cases and even if we dont have a class cached, the lookup in the class-hash is lockless. This change reduces the per-lock dep_map overhead by 56 bytes on 64-bit platforms and by 28 bytes on 32-bit platforms. Signed-off-by:
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