- 15 5月, 2014 12 次提交
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由 Paul E. McKenney 提交于
The original rcu_torture_writer() avoided testing the synchronous grace-period primitives because they were simply wrappers around call_rcu() invocations. The testing of these synchronous primitives was delegated to the fake writers. However, there really is no excuse not to test them, especially in the case of SRCU, where the wrappering is somewhat more elaborate. This commit therefore makes the default rcutorture parameters cause rcu_torture_writer() to include synchronous grace-period primitives in its testing. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Paul E. McKenney 提交于
This commit adds rcutorture testing for get_state_synchronize_rcu() and cond_synchronize_rcu(). Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Paul E. McKenney 提交于
The return value from torture_create_kthread() is currently ignored when creating the rcu_torture_fqs kthread. This commit therefore captures the return value so that it can be tested for errors. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Iulia Manda 提交于
In torture_shuffle_tasks function, the check if an all-zero mask can be passed to set_cpus_allowed_ptr() is redundant after clearing the shuffle_idle_cpu bit. If the mask had more than one bit set, after clearing a bit it has at least one bit set. If the mask had only one bit set, a check is made at the beginning, where the function returns, as there is no need to shuffle only one cpu. Also, this code is executed inside a critical section, delimited by get_online_cpus(), and put_online_cpus(), preventing CPUs from leaving between the check of num_online_cpus and the calls to set_cpus_allowed_ptr() function. Signed-off-by: NIulia Manda <iulia.manda21@gmail.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Paul E. McKenney 提交于
The rcu_torture_reader() function currently uses schedule(). This commit therefore speeds things up a bit by substituting cond_resched(). This change makes rcu_torture_reader() more CPU-bound, so this commit also adjusts the number of readers (the "nreaders" module parameter, which feeds into the "nrealreaders" variable) to allow one CPU to be free of readers on SMP systems. The point of this is to increase the probability that readers will be watching while an updater makes a change. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Paul E. McKenney 提交于
Given a CPU running a loop containing cond_resched(), with no other tasks runnable on that CPU, RCU will eventually report RCU CPU stall warnings due to lack of quiescent states. Fortunately, every call to cond_resched() is a perfectly good quiescent state. Unfortunately, invoking rcu_note_context_switch() is a bit heavyweight for cond_resched(), especially given the need to disable preemption, and, for RCU-preempt, interrupts as well. This commit therefore maintains a per-CPU counter that causes cond_resched(), cond_resched_lock(), and cond_resched_softirq() to call rcu_note_context_switch(), but only about once per 256 invocations. This ratio was chosen in keeping with the relative time constants of RCU grace periods. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Paul E. McKenney 提交于
This commit allows rcutorture to print additional state for the RCU grace-period kthreads in cases where RCU seems reluctant to start a new grace period. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Paul E. McKenney 提交于
This commit adds a call to rcutorture_trace_dump() to dump the ftrace buffer when the RCU grace period stalls in order to help debug the stall. Note that this is different than the RCU CPU stall warning, as it is rcutorture detecting the stall rather than the underlying RCU implementation. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Paul E. McKenney 提交于
Currently, all stuttered kthreads block a jiffy at a time, which can result in them starting at different times. (Note: This is not an energy-efficiency problem unless you run torture tests in production, in which case you have other problems!) This commit increases the intensity of the restart event by causing kthreads to spin through the last jiffy, restarting when they see the variable change. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Paul E. McKenney 提交于
Currently, torture_kthread_stopping() prints only the name of the kthread that is stopping, which can be unedifying. This commit therefore adds "Stopping" to make things more evident. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
The srcu_torture_stats() function prints SRCU's per-CPU c[] array with an unsigned format, which means that the number one less than zero is a very large number. This commit therefore prints this array with a signed format in order to improve readability of the rcutorture output. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
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由 Rashika Kheria 提交于
Mark functions as static in kernel/rcu/torture.c because they are not used outside this file. This eliminates the following warning in kernel/rcu/torture.c: kernel/rcu/torture.c:902:6: warning: no previous prototype for ‘rcutorture_trace_dump’ [-Wmissing-prototypes] kernel/rcu/torture.c:1572:6: warning: no previous prototype for ‘rcu_torture_barrier_cbf’ [-Wmissing-prototypes] Signed-off-by: NRashika Kheria <rashika.kheria@gmail.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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- 14 5月, 2014 2 次提交
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由 Paul E. McKenney 提交于
The current lock_torture_writer() spends too much time sleeping and not enough time hammering locks, as in an eight-CPU test will often only be utilizing a CPU or two. This commit therefore makes lock_torture_writer() sleep less and hammer more. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
The rcutorture output currently does not distinguish between stalls in the RCU implementation and stalls in the rcu_torture_writer() kthreads. This commit therefore adds some diagnostics to help distinguish between these two conditions, at least for the non-SRCU implementations. (SRCU does not provide evidence of update-side forward progress by design.) Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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- 13 4月, 2014 1 次提交
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由 Davidlohr Bueso 提交于
Commits 11d4616b ("futex: revert back to the explicit waiter counting code") and 69cd9eba ("futex: avoid race between requeue and wake") changed some of the finer details of how we think about futexes. One was a late fix and the other a consequence of overlooking the whole requeuing logic. The first change caused our documentation to be incorrect, and the second made us aware that we need to explicitly add more details to it. Signed-off-by: NDavidlohr Bueso <davidlohr@hp.com> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 12 4月, 2014 1 次提交
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由 Al Viro 提交于
that commit has fixed only the parts of that mess in fs/splice.c itself; there had been more in several other ->splice_read() instances... Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 11 4月, 2014 1 次提交
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由 Steven Rostedt (Red Hat) 提交于
The debugfs tracing README file lists all the function triggers except for dump and cpudump. These should be added too. Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
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- 10 4月, 2014 1 次提交
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由 Mathieu Desnoyers 提交于
gcc <= 4.5.x has significant limitations with respect to initialization of anonymous unions within structures. They need to be surrounded by brackets, _and_ they need to be initialized in the same order in which they appear in the structure declaration. Link: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=10676 Link: http://lkml.kernel.org/r/1397077568-3156-1-git-send-email-mathieu.desnoyers@efficios.comSigned-off-by: NMathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
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- 09 4月, 2014 4 次提交
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由 Linus Torvalds 提交于
Jan Stancek reported: "pthread_cond_broadcast/4-1.c testcase from openposix testsuite (LTP) occasionally fails, because some threads fail to wake up. Testcase creates 5 threads, which are all waiting on same condition. Main thread then calls pthread_cond_broadcast() without holding mutex, which calls: futex(uaddr1, FUTEX_CMP_REQUEUE_PRIVATE, 1, 2147483647, uaddr2, ..) This immediately wakes up single thread A, which unlocks mutex and tries to wake up another thread: futex(uaddr2, FUTEX_WAKE_PRIVATE, 1) If thread A manages to call futex_wake() before any waiters are requeued for uaddr2, no other thread is woken up" The ordering constraints for the hash bucket waiter counting are that the waiter counts have to be incremented _before_ getting the spinlock (because the spinlock acts as part of the memory barrier), but the "requeue" operation didn't honor those rules, and nobody had even thought about that case. This fairly simple patch just increments the waiter count for the target hash bucket (hb2) when requeing a futex before taking the locks. It then decrements them again after releasing the lock - the code that actually moves the futex(es) between hash buckets will do the additional required waiter count housekeeping. Reported-and-tested-by: NJan Stancek <jstancek@redhat.com> Acked-by: NDavidlohr Bueso <davidlohr@hp.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org # 3.14 Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Mathieu Desnoyers 提交于
Fix the following sparse warnings: CHECK kernel/tracepoint.c kernel/tracepoint.c:184:18: warning: incorrect type in assignment (different address spaces) kernel/tracepoint.c:184:18: expected struct tracepoint_func *tp_funcs kernel/tracepoint.c:184:18: got struct tracepoint_func [noderef] <asn:4>*funcs kernel/tracepoint.c:216:18: warning: incorrect type in assignment (different address spaces) kernel/tracepoint.c:216:18: expected struct tracepoint_func *tp_funcs kernel/tracepoint.c:216:18: got struct tracepoint_func [noderef] <asn:4>*funcs kernel/tracepoint.c:392:24: error: return expression in void function CC kernel/tracepoint.o kernel/tracepoint.c: In function tracepoint_module_going: kernel/tracepoint.c:491:6: warning: symbol 'syscall_regfunc' was not declared. Should it be static? kernel/tracepoint.c:508:6: warning: symbol 'syscall_unregfunc' was not declared. Should it be static? Link: http://lkml.kernel.org/r/1397049883-28692-1-git-send-email-mathieu.desnoyers@efficios.comSigned-off-by: NMathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
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由 Steven Rostedt (Red Hat) 提交于
Instead of copying the num_tracepoints and tracepoints_ptrs from the module structure to the tp_mod structure, which only uses it to find the module associated to tracepoints of modules that are coming and going, simply copy the pointer to the module struct to the tracepoint tp_module structure. Also removed un-needed brackets around an if statement. Link: http://lkml.kernel.org/r/20140408201705.4dad2c4a@gandalf.local.homeAcked-by: NMathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
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由 Mathieu Desnoyers 提交于
Register/unregister tracepoint probes with struct tracepoint pointer rather than tracepoint name. This change, which vastly simplifies tracepoint.c, has been proposed by Steven Rostedt. It also removes 8.8kB (mostly of text) to the vmlinux size. From this point on, the tracers need to pass a struct tracepoint pointer to probe register/unregister. A probe can now only be connected to a tracepoint that exists. Moreover, tracers are responsible for unregistering the probe before the module containing its associated tracepoint is unloaded. text data bss dec hex filename 10443444 4282528 10391552 25117524 17f4354 vmlinux.orig 10434930 4282848 10391552 25109330 17f2352 vmlinux Link: http://lkml.kernel.org/r/1396992381-23785-2-git-send-email-mathieu.desnoyers@efficios.com CC: Ingo Molnar <mingo@kernel.org> CC: Frederic Weisbecker <fweisbec@gmail.com> CC: Andrew Morton <akpm@linux-foundation.org> CC: Frank Ch. Eigler <fche@redhat.com> CC: Johannes Berg <johannes.berg@intel.com> Signed-off-by: NMathieu Desnoyers <mathieu.desnoyers@efficios.com> [ SDR - fixed return val in void func in tracepoint_module_going() ] Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
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- 08 4月, 2014 18 次提交
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由 Josh Triplett 提交于
When the system has only one CPU, lglock is effectively a spinlock; map it directly to spinlock to eliminate the indirection and duplicate code. In addition to removing overhead, this drops 1.6k of code with a defconfig modified to have !CONFIG_SMP, and 1.1k with a minimal config. Signed-off-by: NJosh Triplett <josh@joshtriplett.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Michal Marek <mmarek@suse.cz> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: David Howells <dhowells@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Nick Piggin <npiggin@kernel.dk> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Christoph Lameter 提交于
The initialization of a structure is not subject to synchronization. The use of __this_cpu would trigger a false positive with the additional preemption checks for __this_cpu ops. So simply disable the check through the use of raw_cpu ops. Trace: __this_cpu_write operation in preemptible [00000000] code: modprobe/286 caller is __this_cpu_preempt_check+0x38/0x60 CPU: 3 PID: 286 Comm: modprobe Tainted: GF 3.12.0-rc4+ #187 Call Trace: dump_stack+0x4e/0x82 check_preemption_disabled+0xec/0x110 __this_cpu_preempt_check+0x38/0x60 load_module+0xcfd/0x2650 SyS_init_module+0xa6/0xd0 tracesys+0xe1/0xe6 Signed-off-by: NChristoph Lameter <cl@linux.com> Acked-by: NIngo Molnar <mingo@kernel.org> Acked-by: NRusty Russell <rusty@rustcorp.com.au> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Gideon Israel Dsouza 提交于
To increase compiler portability there is <linux/compiler.h> which provides convenience macros for various gcc constructs. Eg: __weak for __attribute__((weak)). I've replaced all instances of gcc attributes with the right macro in the kernel subsystem. Signed-off-by: NGideon Israel Dsouza <gidisrael@gmail.com> Cc: "Rafael J. Wysocki" <rjw@sisk.pl> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Fabian Frederick 提交于
Currently, booting without initrd specified on 80x25 screen gives a call trace followed by atkbd : Spurious ACK. Original message ("VFS: Unable to mount root fs") is not available. Of course this could happen in other situations... This patch displays panic reason after call trace which could help lot of people even if it's not the very last line on screen. Also, convert all panic.c printk(KERN_EMERG to pr_emerg( [akpm@linux-foundation.org: missed a couple of pr_ conversions] Signed-off-by: NFabian Frederick <fabf@skynet.be> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Liu Hua 提交于
As sysctl_hung_task_timeout_sec is unsigned long, when this value is larger then LONG_MAX/HZ, the function schedule_timeout_interruptible in watchdog will return immediately without sleep and with print : schedule_timeout: wrong timeout value ffffffffffffff83 and then the funtion watchdog will call schedule_timeout_interruptible again and again. The screen will be filled with "schedule_timeout: wrong timeout value ffffffffffffff83" This patch does some check and correction in sysctl, to let the function schedule_timeout_interruptible allways get the valid parameter. Signed-off-by: NLiu Hua <sdu.liu@huawei.com> Tested-by: NSatoru Takeuchi <satoru.takeuchi@gmail.com> Cc: <stable@vger.kernel.org> [3.4+] Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Oleg Nesterov 提交于
Even if the main thread is dead the process still can stop/continue. However, if the leader is ptraced wait_consider_task(ptrace => false) always skips wait_task_stopped/wait_task_continued, so WSTOPPED or WCONTINUED can never work for the natural parent in this case. Move the "A zombie ptracee is only visible to its ptracer" check into the "if (!delay_group_leader(p))" block. ->notask_error is cleared by the "fall through" code below. This depends on the previous change, wait_task_stopped/continued must be avoided if !delay_group_leader() and the tracer is ->real_parent. Otherwise WSTOPPED|WEXITED could wrongly report "stopped" when the child is already dead (single-threaded or not). If it is traced by another task then the "stopped" state is fine until the debugger detaches and reveals a zombie state. Stupid test-case: void *tfunc(void *arg) { sleep(1); // wait for zombie leader raise(SIGSTOP); exit(0x13); return NULL; } int run_child(void) { pthread_t thread; if (!fork()) { int tracee = getppid(); assert(ptrace(PTRACE_ATTACH, tracee, 0,0) == 0); do ptrace(PTRACE_CONT, tracee, 0,0); while (wait(NULL) > 0); return 0; } sleep(1); // wait for PTRACE_ATTACH assert(pthread_create(&thread, NULL, tfunc, NULL) == 0); pthread_exit(NULL); } int main(void) { int child, stat; child = fork(); if (!child) return run_child(); assert(child == waitpid(-1, &stat, WSTOPPED)); assert(stat == 0x137f); kill(child, SIGCONT); assert(child == waitpid(-1, &stat, WCONTINUED)); assert(stat == 0xffff); assert(child == waitpid(-1, &stat, 0)); assert(stat == 0x1300); return 0; } Without this patch it hangs in waitpid(WSTOPPED), wait_task_stopped() is never called. Note: this doesn't fix all problems with a zombie delay_group_leader(), WCONTINUED | WEXITED check is not exactly right. debugger can't assume it will be notified if another thread reaps the whole thread group. Signed-off-by: NOleg Nesterov <oleg@redhat.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Cc: Lennart Poettering <lpoetter@redhat.com> Cc: Michal Schmidt <mschmidt@redhat.com> Cc: Roland McGrath <roland@hack.frob.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Oleg Nesterov 提交于
"A zombie is only visible to its ptracer" logic in wait_consider_task() is very wrong. Trivial test-case: #include <unistd.h> #include <sys/ptrace.h> #include <sys/wait.h> #include <assert.h> int main(void) { int child = fork(); if (!child) { assert(ptrace(PTRACE_TRACEME, 0,0,0) == 0); return 0x23; } assert(waitid(P_ALL, child, NULL, WEXITED | WNOWAIT) == 0); assert(waitid(P_ALL, 0, NULL, WSTOPPED) == -1); return 0; } it hangs in waitpid(WSTOPPED) despite the fact it has a single zombie child. This is because wait_consider_task(ptrace => 0) sees p->ptrace and cleares ->notask_error assuming that the debugger should detach and notify us. Change wait_consider_task(ptrace => 0) to pretend that ptrace == T if the child is traced by us. This really simplifies the logic and allows us to do more fixes, see the next changes. This also hides the unwanted group stop state automatically, we can remove another ptrace_reparented() check. Unfortunately, this adds the following behavioural changes: 1. Before this patch wait(WEXITED | __WNOTHREAD) does not reap a natural child if it is traced by the caller's sub-thread. Hopefully nobody will ever notice this change, and I think that nobody should rely on this behaviour anyway. 2. SIGNAL_STOP_CONTINUED is no longer hidden from debugger if it is real parent. While this change comes as a side effect, I think it is good by itself. The group continued state can not be consumed by another process in this case, it doesn't depend on ptrace, it doesn't make sense to hide it from real parent. Perhaps we should add the thread_group_leader() check before wait_task_continued()? May be, but this shouldn't depend on ptrace_reparented(). Signed-off-by: NOleg Nesterov <oleg@redhat.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Cc: Lennart Poettering <lpoetter@redhat.com> Cc: Michal Schmidt <mschmidt@redhat.com> Cc: Roland McGrath <roland@hack.frob.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Oleg Nesterov 提交于
Now that EXIT_DEAD is the terminal state it doesn't make sense to call eligible_child() or security_task_wait() if the task is really dead. Signed-off-by: NOleg Nesterov <oleg@redhat.com> Tested-by: NMichal Schmidt <mschmidt@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Lennart Poettering <lpoetter@redhat.com> Cc: Roland McGrath <roland@hack.frob.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Oleg Nesterov 提交于
wait_task_zombie() always uses EXIT_TRACE/ptrace_unlink() if ptrace_reparented(). This is suboptimal and a bit confusing: we do not need do_notify_parent(p) if !thread_group_leader(p) and in this case we also do not need ptrace_unlink(), we can rely on ptrace_release_task(). Change wait_task_zombie() to check thread_group_leader() along with ptrace_reparented() and simplify the final p->exit_state transition. Signed-off-by: NOleg Nesterov <oleg@redhat.com> Tested-by: NMichal Schmidt <mschmidt@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Lennart Poettering <lpoetter@redhat.com> Cc: Roland McGrath <roland@hack.frob.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Oleg Nesterov 提交于
wait_task_zombie() first does EXIT_ZOMBIE->EXIT_DEAD transition and drops tasklist_lock. If this task is not the natural child and it is traced, we change its state back to EXIT_ZOMBIE for ->real_parent. The last transition is racy, this is even documented in 50b8d257 "ptrace: partially fix the do_wait(WEXITED) vs EXIT_DEAD->EXIT_ZOMBIE race". wait_consider_task() tries to detect this transition and clear ->notask_error but we can't rely on ptrace_reparented(), debugger can exit and do ptrace_unlink() before its sub-thread sets EXIT_ZOMBIE. And there is another problem which were missed before: this transition can also race with reparent_leader() which doesn't reset >exit_signal if EXIT_DEAD, assuming that this task must be reaped by someone else. So the tracee can be re-parented with ->exit_signal != SIGCHLD, and if /sbin/init doesn't use __WALL it becomes unreapable. This was fixed by the previous commit, but it was the temporary hack. 1. Add the new exit_state, EXIT_TRACE. It means that the task is the traced zombie, debugger is going to detach and notify its natural parent. This new state is actually EXIT_ZOMBIE | EXIT_DEAD. This way we can avoid the changes in proc/kgdb code, get_task_state() still reports "X (dead)" in this case. Note: with or without this change userspace can see Z -> X -> Z transition. Not really bad, but probably makes sense to fix. 2. Change wait_task_zombie() to use EXIT_TRACE instead of EXIT_DEAD if we need to notify the ->real_parent. 3. Revert the previous hack in reparent_leader(), now that EXIT_DEAD is always the final state we can safely ignore such a task. 4. Change wait_consider_task() to check EXIT_TRACE separately and kill the racy and no longer needed ptrace_reparented() case. If ptrace == T an EXIT_TRACE thread should be simply ignored, the owner of this state is going to ptrace_unlink() this task. We can pretend that it was already removed from ->ptraced list. Otherwise we should skip this thread too but clear ->notask_error, we must be the natural parent and debugger is going to untrace and notify us. IOW, this doesn't differ from "EXIT_ZOMBIE && p->ptrace" even if the task was already untraced. Signed-off-by: NOleg Nesterov <oleg@redhat.com> Reported-by: NJan Kratochvil <jan.kratochvil@redhat.com> Reported-by: NMichal Schmidt <mschmidt@redhat.com> Tested-by: NMichal Schmidt <mschmidt@redhat.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Lennart Poettering <lpoetter@redhat.com> Cc: Roland McGrath <roland@hack.frob.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Oleg Nesterov 提交于
wait_task_zombie() first does EXIT_ZOMBIE->EXIT_DEAD transition and drops tasklist_lock. If this task is not the natural child and it is traced, we change its state back to EXIT_ZOMBIE for ->real_parent. The last transition is racy, this is even documented in 50b8d257 "ptrace: partially fix the do_wait(WEXITED) vs EXIT_DEAD->EXIT_ZOMBIE race". wait_consider_task() tries to detect this transition and clear ->notask_error but we can't rely on ptrace_reparented(), debugger can exit and do ptrace_unlink() before its sub-thread sets EXIT_ZOMBIE. And there is another problem which were missed before: this transition can also race with reparent_leader() which doesn't reset >exit_signal if EXIT_DEAD, assuming that this task must be reaped by someone else. So the tracee can be re-parented with ->exit_signal != SIGCHLD, and if /sbin/init doesn't use __WALL it becomes unreapable. Change reparent_leader() to update ->exit_signal even if EXIT_DEAD. Note: this is the simple temporary hack for -stable, it doesn't try to solve all problems, it will be reverted by the next changes. Signed-off-by: NOleg Nesterov <oleg@redhat.com> Reported-by: NJan Kratochvil <jan.kratochvil@redhat.com> Reported-by: NMichal Schmidt <mschmidt@redhat.com> Tested-by: NMichal Schmidt <mschmidt@redhat.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Lennart Poettering <lpoetter@redhat.com> Cc: Roland McGrath <roland@hack.frob.com> Cc: Tejun Heo <tj@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Guillaume Morin 提交于
The process events connector delivers a notification when a process exits. This is really convenient for a process that spawns and wants to monitor its children through an epoll-able() interface. Unfortunately, there is a small window between when the event is delivered and the child become wait()-able. This is creates a race if the parent wants to make sure that it knows about the exit, e.g pid_t pid = fork(); if (pid > 0) { register_interest_for_pid(pid); if (waitpid(pid, NULL, WNOHANG) > 0) { /* We might have raced with exit() */ } return; } /* Child */ execve(...) register_interest_for_pid() would be telling the the connector socket reader to pay attention to events related to pid. Though this is not a bug, I think it would make the connector a bit more usable if this race was closed by simply moving the call to proc_exit_connector() from just before exit_notify() to right after. Oleg said: : Even with this patch the code above is still "racy" if the child is : multi-threaded. Plus it should obviously filter-out subthreads. And : afaics there is no way to make it reliable, even if you change the code : above so that waitpid() is called only after the last thread exits WNOHANG : still can fail. Signed-off-by: NGuillaume Morin <guillaume@morinfr.org> Cc: Matt Helsley <matt.helsley@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: David S. Miller <davem@davemloft.net> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Oleg Nesterov 提交于
It is not clear why check_stack_usage() is called so early and thus it never checks the stack usage in, say, exit_notify() or flush_ptrace_hw_breakpoint() or other functions which are only called by do_exit(). Move the callsite down to the last preempt_disable/schedule. Signed-off-by: NOleg Nesterov <oleg@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Oleg Nesterov 提交于
Commit 8aac6270 ("move exit_task_namespaces() outside of exit_notify()") breaks pppd and the exiting service crashes the kernel: BUG: unable to handle kernel NULL pointer dereference at 0000000000000028 IP: ppp_register_channel+0x13/0x20 [ppp_generic] Call Trace: ppp_asynctty_open+0x12b/0x170 [ppp_async] tty_ldisc_open.isra.2+0x27/0x60 tty_ldisc_hangup+0x1e3/0x220 __tty_hangup+0x2c4/0x440 disassociate_ctty+0x61/0x270 do_exit+0x7f2/0xa50 ppp_register_channel() needs ->net_ns and current->nsproxy == NULL. Move disassociate_ctty() before exit_task_namespaces(), it doesn't make sense to delay it after perf_event_exit_task() or cgroup_exit(). This also allows to use task_work_add() inside the (nontrivial) code paths in disassociate_ctty(). Investigated by Peter Hurley. Signed-off-by: NOleg Nesterov <oleg@redhat.com> Reported-by: NSree Harsha Totakura <sreeharsha@totakura.in> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: Sree Harsha Totakura <sreeharsha@totakura.in> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Jeff Dike <jdike@addtoit.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Andrey Vagin <avagin@openvz.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: <stable@vger.kernel.org> [v3.10+] Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 David Rientjes 提交于
The res_counter_{charge,uncharge}_locked() variants are not used in the kernel outside of the resource counter code itself, so remove the interface. Signed-off-by: NDavid Rientjes <rientjes@google.com> Acked-by: NMichal Hocko <mhocko@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Pekka Enberg <penberg@kernel.org> Cc: Tejun Heo <tj@kernel.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Jianguo Wu <wujianguo@huawei.com> Cc: Tim Hockin <thockin@google.com> Cc: Christoph Lameter <cl@linux.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 David Rientjes 提交于
PF_MEMPOLICY is an unnecessary optimization for CONFIG_SLAB users. There's no significant performance degradation to checking current->mempolicy rather than current->flags & PF_MEMPOLICY in the allocation path, especially since this is considered unlikely(). Running TCP_RR with netperf-2.4.5 through localhost on 16 cpu machine with 64GB of memory and without a mempolicy: threads before after 16 1249409 1244487 32 1281786 1246783 48 1239175 1239138 64 1244642 1241841 80 1244346 1248918 96 1266436 1254316 112 1307398 1312135 128 1327607 1326502 Per-process flags are a scarce resource so we should free them up whenever possible and make them available. We'll be using it shortly for memcg oom reserves. Signed-off-by: NDavid Rientjes <rientjes@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Pekka Enberg <penberg@kernel.org> Cc: Tejun Heo <tj@kernel.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Jianguo Wu <wujianguo@huawei.com> Cc: Tim Hockin <thockin@google.com> Cc: Christoph Lameter <cl@linux.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 David Rientjes 提交于
copy_flags() does not use the clone_flags formal and can be collapsed into copy_process() for cleaner code. Signed-off-by: NDavid Rientjes <rientjes@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Pekka Enberg <penberg@kernel.org> Cc: Tejun Heo <tj@kernel.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Jianguo Wu <wujianguo@huawei.com> Cc: Tim Hockin <thockin@google.com> Cc: Christoph Lameter <cl@linux.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Davidlohr Bueso 提交于
This patch is a continuation of efforts trying to optimize find_vma(), avoiding potentially expensive rbtree walks to locate a vma upon faults. The original approach (https://lkml.org/lkml/2013/11/1/410), where the largest vma was also cached, ended up being too specific and random, thus further comparison with other approaches were needed. There are two things to consider when dealing with this, the cache hit rate and the latency of find_vma(). Improving the hit-rate does not necessarily translate in finding the vma any faster, as the overhead of any fancy caching schemes can be too high to consider. We currently cache the last used vma for the whole address space, which provides a nice optimization, reducing the total cycles in find_vma() by up to 250%, for workloads with good locality. On the other hand, this simple scheme is pretty much useless for workloads with poor locality. Analyzing ebizzy runs shows that, no matter how many threads are running, the mmap_cache hit rate is less than 2%, and in many situations below 1%. The proposed approach is to replace this scheme with a small per-thread cache, maximizing hit rates at a very low maintenance cost. Invalidations are performed by simply bumping up a 32-bit sequence number. The only expensive operation is in the rare case of a seq number overflow, where all caches that share the same address space are flushed. Upon a miss, the proposed replacement policy is based on the page number that contains the virtual address in question. Concretely, the following results are seen on an 80 core, 8 socket x86-64 box: 1) System bootup: Most programs are single threaded, so the per-thread scheme does improve ~50% hit rate by just adding a few more slots to the cache. +----------------+----------+------------------+ | caching scheme | hit-rate | cycles (billion) | +----------------+----------+------------------+ | baseline | 50.61% | 19.90 | | patched | 73.45% | 13.58 | +----------------+----------+------------------+ 2) Kernel build: This one is already pretty good with the current approach as we're dealing with good locality. +----------------+----------+------------------+ | caching scheme | hit-rate | cycles (billion) | +----------------+----------+------------------+ | baseline | 75.28% | 11.03 | | patched | 88.09% | 9.31 | +----------------+----------+------------------+ 3) Oracle 11g Data Mining (4k pages): Similar to the kernel build workload. +----------------+----------+------------------+ | caching scheme | hit-rate | cycles (billion) | +----------------+----------+------------------+ | baseline | 70.66% | 17.14 | | patched | 91.15% | 12.57 | +----------------+----------+------------------+ 4) Ebizzy: There's a fair amount of variation from run to run, but this approach always shows nearly perfect hit rates, while baseline is just about non-existent. The amounts of cycles can fluctuate between anywhere from ~60 to ~116 for the baseline scheme, but this approach reduces it considerably. For instance, with 80 threads: +----------------+----------+------------------+ | caching scheme | hit-rate | cycles (billion) | +----------------+----------+------------------+ | baseline | 1.06% | 91.54 | | patched | 99.97% | 14.18 | +----------------+----------+------------------+ [akpm@linux-foundation.org: fix nommu build, per Davidlohr] [akpm@linux-foundation.org: document vmacache_valid() logic] [akpm@linux-foundation.org: attempt to untangle header files] [akpm@linux-foundation.org: add vmacache_find() BUG_ON] [hughd@google.com: add vmacache_valid_mm() (from Oleg)] [akpm@linux-foundation.org: coding-style fixes] [akpm@linux-foundation.org: adjust and enhance comments] Signed-off-by: NDavidlohr Bueso <davidlohr@hp.com> Reviewed-by: NRik van Riel <riel@redhat.com> Acked-by: NLinus Torvalds <torvalds@linux-foundation.org> Reviewed-by: NMichel Lespinasse <walken@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Tested-by: NHugh Dickins <hughd@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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