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    <blockquote> <p>what do we mean by thread running in User mode and running in kernel mode?</p> </blockquote> <p>There is no way to know what a person means by a phrase without context. If I had to guess, I'd say they are talking about whether the thread is scheduled by a user-space scheduler or a kernel scheduler. But it's also possible they are actually asking whether the thread is running user code or kernel code.</p> <blockquote> <p>Is this related to thread execution instruction from User mode and thread executing instruction from Kernel mode? Kindly elaborate.</p> </blockquote> <p>It could be. It also might not be. There's no way to know what a person means by a phrase without context.</p> <blockquote> <p>Also, is it possible that if a thread is executing in user mode is put to suspended state, then it may start executing in kernel mode? if yes, how is it possible?</p> </blockquote> <p>For implementations where the kernel schedules threads, the scheduler is running in kernel space. The code that actually suspends the thread typically runs in kernel space too because it has to add the thread to the various kernel scheduler data structures. So the thread that resumes the thread will run in kernel space too. At a higher level view, the same thread of execution can "become" the kernel scheduler, choose a user-space thread to execute, and then "become" that thread.</p> <blockquote> <p>Until now I am only aware that a thread if suspended will be SUSPENDED completely, i.e. the context switch will take place by CPU to schedule another thread.</p> </blockquote> <p>Right, and that's kernel code. So the same core is running user space code, then it's running kernel code, then it's running the user space code of another thread.</p>
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    1. POThreads in User and kernel mode
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    1. USDavid Schwartz
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    1. POThreads in User and kernel mode
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    1. COThanks David for your response. I am sorry for this hanging context. Now, after reading your reply my question is what are these two modes? how do they differ and what they contain? Consider that my context is related to User mode synchronization and kernel mode synchronization. Why so, because some blog say that when executing in user mode its faster than kernel mode and also switching b/w these modes takes some time. So question is, why are these two modes, what they contains and where in address space do the two part of code gets loaded.
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      1. USBhupesh Pant
 

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