On Wed, Jan 28, 2015 at 9:56 PM, Sreejith M M <sreejith.mm@xxxxxxxxx> wrote:
Hi,
I was trying to understand the difference in scheduling between
processes and threads(belong to same process).
I was thinking that, when kernel has to switch to a task which belong
to the same process, it does not have to clear / replace page global
directories and other memory related information.
But in switch_mm function some code is put under CONFIG_SMP function.
What is its signigicance? Code is
below(http://lxr.free-electrons.com/source/arch/x86/include/asm/mmu_context.h#L37)
.
What I infer is that the code is doing flush tlb, reload page table
directories etc in multiprocessor mode(obviously) but I believe this
code may never be executed .
Can anyone help to understand what this part of the function supposed to do?
60 #ifdef CONFIG_SMP
61 else {
62 this_cpu_write(cpu_tlbstate.state, TLBSTATE_OK);
63 BUG_ON(this_cpu_read(cpu_tlbstate.active_mm) != next);
64
65 if (!cpumask_test_cpu(cpu, mm_cpumask(next))) {
66 /*
67 * On established mms, the mm_cpumask is
only changed
68 * from irq context, from
ptep_clear_flush() while in
69 * lazy tlb mode, and here. Irqs are blocked during
70 * schedule, protecting us from
simultaneous changes.
71 */
72 cpumask_set_cpu(cpu, mm_cpumask(next));
73 /*
74 * We were in lazy tlb mode and leave_mm disabled
75 * tlb flush IPI delivery. We must reload CR3
76 * to make sure to use no freed page tables.
77 */
78 load_cr3(next->pgd);
79 trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH,
TLB_FLUSH_ALL);
80 load_LDT_nolock(&next->context);
81 }
82 }
83 #endif
--
Regards,
Sreejith
Hi ,
can someone please give me any answers for this?
--
Regards,
Sreejith
Sreejith
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