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a64f42d1df
Currently, the sched code checks if the rq clock has been
updated after its lock has been held when CONFIG_SCHED_DEBUG
is enabled. It tracks this by clearing the RQCF_UPDATED bit
when a lock is acquired and setting it upon a subsequent
update_rq_clock() call. It warns if rq clock is read without
RQCF_UPDATED flag indicating the code path missed updating
the clock.
When migrate_tasks() is called during a pause_cpus() event,
the local variable orf is updated with the contents of *rf,
prior to the call to update_rq_clock(). As a result, when
migrate_tasks() restores *rf from the local variable the
RQCF_UPDATED flag is lost. This clearing out of the
RQCF_UPDATED flag leads to a warning when the next task
is being pushed out.
For example in migrate_tasks()
orf = rf; // save flags, RQCF_UPDATE cleared
update_rq_clock() // set RQCF_UPDATE
for()
...
__migrate_task(dead_rq, new_cpu)
...
--> if migration, restore dead_rq's flags with orf.
--> We loose RQCF_UPDATE
rq_relock(dead_rq, orf)
This leaves the current cpu's rq clock_update_flags with the
RQCF_UPDATED flag cleared, an error condition with
CONFIG_SCHED_DEBUG enabled.
Fix the issue for by ensuring that the local variable orf
has the RQCF_UPDATED flag set, allowing the current
CPU's rq to have the flag set and leaving it in a good state
for future usage.
pause_cpus() is currently Android specific. As cpu_pause does
not rely on stop_machine_cpuslocked() like the regular
hotunplug path does, there's a risk for another CPU to
read the rq_clock, after we cleared RQCF_UPDATE, when using
pause_cpus(). This change will have little or no impact outside
of Android currently. If pause_cpus() or drain_rq_cpu_stop()
are merged upstream this change should be merged as well.
Bug: 186222712
Change-Id: Id241122e1449cdd4dcd15f94eb68735b40e3d6f5
Signed-off-by: Stephen Dickey <dickey@codeaurora.org>
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| bpf | ||
| cgroup | ||
| configs | ||
| debug | ||
| dma | ||
| entry | ||
| events | ||
| gcov | ||
| irq | ||
| kcsan | ||
| livepatch | ||
| locking | ||
| power | ||
| printk | ||
| rcu | ||
| sched | ||
| time | ||
| trace | ||
| .gitignore | ||
| acct.c | ||
| async.c | ||
| audit_fsnotify.c | ||
| audit_tree.c | ||
| audit_watch.c | ||
| audit.c | ||
| audit.h | ||
| auditfilter.c | ||
| auditsc.c | ||
| backtracetest.c | ||
| bounds.c | ||
| capability.c | ||
| cfi.c | ||
| compat.c | ||
| configs.c | ||
| context_tracking.c | ||
| cpu_pm.c | ||
| cpu.c | ||
| crash_core.c | ||
| crash_dump.c | ||
| cred.c | ||
| delayacct.c | ||
| dma.c | ||
| exec_domain.c | ||
| exit.c | ||
| extable.c | ||
| fail_function.c | ||
| fork.c | ||
| freezer.c | ||
| futex.c | ||
| gen_kheaders.sh | ||
| groups.c | ||
| hung_task.c | ||
| iomem.c | ||
| irq_work.c | ||
| jump_label.c | ||
| kallsyms.c | ||
| kcmp.c | ||
| Kconfig.freezer | ||
| Kconfig.hz | ||
| Kconfig.locks | ||
| Kconfig.preempt | ||
| kcov.c | ||
| kexec_core.c | ||
| kexec_elf.c | ||
| kexec_file.c | ||
| kexec_internal.h | ||
| kexec.c | ||
| kheaders.c | ||
| kmod.c | ||
| kprobes.c | ||
| ksysfs.c | ||
| kthread.c | ||
| latencytop.c | ||
| Makefile | ||
| module_signature.c | ||
| module_signing.c | ||
| module-internal.h | ||
| module.c | ||
| notifier.c | ||
| nsproxy.c | ||
| padata.c | ||
| panic.c | ||
| params.c | ||
| pid_namespace.c | ||
| pid.c | ||
| profile.c | ||
| ptrace.c | ||
| range.c | ||
| reboot.c | ||
| regset.c | ||
| relay.c | ||
| resource.c | ||
| rseq.c | ||
| scftorture.c | ||
| scs.c | ||
| seccomp.c | ||
| signal.c | ||
| smp.c | ||
| smpboot.c | ||
| smpboot.h | ||
| softirq.c | ||
| stackleak.c | ||
| stacktrace.c | ||
| static_call.c | ||
| stop_machine.c | ||
| sys_ni.c | ||
| sys.c | ||
| sysctl-test.c | ||
| sysctl.c | ||
| task_work.c | ||
| taskstats.c | ||
| test_kprobes.c | ||
| torture.c | ||
| tracepoint.c | ||
| tsacct.c | ||
| ucount.c | ||
| uid16.c | ||
| uid16.h | ||
| umh.c | ||
| up.c | ||
| user_namespace.c | ||
| user-return-notifier.c | ||
| user.c | ||
| usermode_driver.c | ||
| utsname_sysctl.c | ||
| utsname.c | ||
| watch_queue.c | ||
| watchdog_hld.c | ||
| watchdog.c | ||
| workqueue_internal.h | ||
| workqueue.c | ||