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--- mywiki:linux:linux_kernel_notes [2015/04/02 15:03] – created shaoguoh
+++ mywiki:linux:linux_kernel_notes [2019/09/15 18:55] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
-|  | IRQ Handler A | IRQ Handler B | Softirq A | Softirq B | Tasklet A | Tasklet B | Timer A | Timer B | User Context A | User Context B |
+| [[http://www.linux-mips.org/wiki/Linux/MIPS_Porting_Guide|MIPS Porting Guide]] |
-| IRQ Handler A | None |
+===== Kernel Context knowledge =====
-| IRQ Handler B | spin_lock_irqsave() | None |
+| process context | includes user context, kernel thread, work queue |
-Softirq A spin_lock_irq() spin_lock_irq() spin_lock()
+| User Context | The kernel executing on behalf of a particular process (ie. a system call or trap, ioctl, module_init, module_exit or kernel thread, workqueue. You can tell which process with the current macro.) Not to be confused with userspace. Can be interrupted by software or hardware interrupts. |
-Softirq B spin_lock_irq() spin_lock_irq() spin_lock() spin_lock()
+| Userspace (not kernel) | A process executing its own code outside the kernel |
-Tasklet A spin_lock_irq() spin_lock_irq() spin_lock() spin_lock() None
+| Interrupt context | includes hard irq, kernel timer, softirq, tasklet | if in_interrupt() true |
-Tasklet B spin_lock_irq() spin_lock_irq() spin_lock() spin_lock() spin_lock() None
+| Hardware IRQ | Hardware interrupt request | if in_irq() true |
-Timer A spin_lock_irq() spin_lock_irq() spin_lock() spin_lock() spin_lock() spin_lock() None
+| Softirq | Software interrupt handler. in_irq() returns false; in_softirq() returns true. Tasklets and softirqs both fall into the category of 'software interrupts'. Strictly speaking a softirq is one of up to 32 enumerated software interrupts which can run on multiple CPUs at once. Sometimes used to refer to tasklets as well (ie. all software interrupts). | if in_irq() false and in_softirq() true |
-Timer B spin_lock_irq() spin_lock_irq() spin_lock() spin_lock() spin_lock() spin_lock() spin_lock() None
+| Tasklet | A dynamically-registered software interrupt, which is guaranteed to only run on one CPU at a time |
-User Context A spin_lock_irq() spin_lock_irq() spin_lock_bh() spin_lock_bh() spin_lock_bh() spin_lock_bh() spin_lock_bh() spin_lock_bh() None
+| Timer | which is running at (or close to) a given time. When running, it is just like a tasklet (in fact, they are called from the TIMER_SOFTIRQ). |
-User Context B spin_lock_irq() spin_lock_irq() spin_lock_bh() spin_lock_bh() spin_lock_bh() spin_lock_bh() spin_lock_bh() spin_lock_bh() down_interruptible None