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| author | Maksim Rayskiy <mrayskiy@broadcom.com> | 2011-02-12 10:21:32 -0800 |
|---|---|---|
| committer | Ralf Baechle <ralf@linux-mips.org> | 2011-03-14 21:07:27 +0100 |
| commit | 6667deb69ee3b8a31ea88e1303cf3ad7d4f221da (patch) | |
| tree | 575e660bec3cdb905f31940ab3ca64d7185202be | |
| parent | ba9786f32473410bbec256db9745a7fbcaace69f (diff) | |
| download | linux-6667deb69ee3b8a31ea88e1303cf3ad7d4f221da.tar.gz | |
MIPS: Move idle task creation to work queue
To avoid forking usermode thread when creating an idle task, move fork_idle to a work queue. If kernel starts with maxcpus= option which does not bring all available cpus online at boot time, idle tasks for offline cpus are not created. If later offline cpus are hotplugged through sysfs, __cpu_up is called in the context of the user task, and fork_idle copies its non-zero mm pointer. This causes BUG() in per_cpu_trap_init. This also avoids issues with resource limits of the CPU writing to sysfs, containers, maybe others. Signed-off-by: Maksim Rayskiy <mrayskiy@broadcom.com> To: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/2070/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
| -rw-r--r-- | arch/mips/kernel/smp.c | 31 |
1 files changed, 29 insertions, 2 deletions
diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c index 383aeb95cb49..32a256101082 100644 --- a/arch/mips/kernel/smp.c +++ b/arch/mips/kernel/smp.c @@ -193,6 +193,22 @@ void __devinit smp_prepare_boot_cpu(void) */ static struct task_struct *cpu_idle_thread[NR_CPUS]; +struct create_idle { + struct work_struct work; + struct task_struct *idle; + struct completion done; + int cpu; +}; + +static void __cpuinit do_fork_idle(struct work_struct *work) +{ + struct create_idle *c_idle = + container_of(work, struct create_idle, work); + + c_idle->idle = fork_idle(c_idle->cpu); + complete(&c_idle->done); +} + int __cpuinit __cpu_up(unsigned int cpu) { struct task_struct *idle; @@ -203,8 +219,19 @@ int __cpuinit __cpu_up(unsigned int cpu) * Linux can schedule processes on this slave. */ if (!cpu_idle_thread[cpu]) { - idle = fork_idle(cpu); - cpu_idle_thread[cpu] = idle; + /* + * Schedule work item to avoid forking user task + * Ported from arch/x86/kernel/smpboot.c + */ + struct create_idle c_idle = { + .cpu = cpu, + .done = COMPLETION_INITIALIZER_ONSTACK(c_idle.done), + }; + + INIT_WORK_ONSTACK(&c_idle.work, do_fork_idle); + schedule_work(&c_idle.work); + wait_for_completion(&c_idle.done); + idle = cpu_idle_thread[cpu] = c_idle.idle; if (IS_ERR(idle)) panic(KERN_ERR "Fork failed for CPU %d", cpu); |