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commitc0f7f5b6c6upstream. gpstate_timer_handler() uses synchronous smp_call to set the pstate on the requested core. This causes the below hard lockup: smp_call_function_single+0x110/0x180 (unreliable) smp_call_function_any+0x180/0x250 gpstate_timer_handler+0x1e8/0x580 call_timer_fn+0x50/0x1c0 expire_timers+0x138/0x1f0 run_timer_softirq+0x1e8/0x270 __do_softirq+0x158/0x3e4 irq_exit+0xe8/0x120 timer_interrupt+0x9c/0xe0 decrementer_common+0x114/0x120 -- interrupt: 901 at doorbell_global_ipi+0x34/0x50 LR = arch_send_call_function_ipi_mask+0x120/0x130 arch_send_call_function_ipi_mask+0x4c/0x130 smp_call_function_many+0x340/0x450 pmdp_invalidate+0x98/0xe0 change_huge_pmd+0xe0/0x270 change_protection_range+0xb88/0xe40 mprotect_fixup+0x140/0x340 SyS_mprotect+0x1b4/0x350 system_call+0x58/0x6c One way to avoid this is removing the smp-call. We can ensure that the timer always runs on one of the policy-cpus. If the timer gets migrated to a cpu outside the policy then re-queue it back on the policy->cpus. This way we can get rid of the smp-call which was being used to set the pstate on the policy->cpus. Fixes:7bc54b652f("timers, cpufreq/powernv: Initialize the gpstate timer as pinned") Cc: stable@vger.kernel.org # v4.8+ Reported-by: Nicholas Piggin <npiggin@gmail.com> Reported-by: Pridhiviraj Paidipeddi <ppaidipe@linux.vnet.ibm.com> Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> Acked-by: Nicholas Piggin <npiggin@gmail.com> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Acked-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.