On Thu, May 9, 2024 at 8:39 AM Muni Sekhar <munisekharrms@xxxxxxxxx> wrote: > > Dear Linux Kernel Community, > > I am reaching out to seek assistance regarding the usage of spin locks > in the Linux kernel and to address a recurring issue related to hard > LOCKUP errors that I have encountered during testing. > build your kernel with LOCKDEP everything ? > Recently, I developed a small kernel module that involves ISR handling > and utilizes the spinlock_t primitive. In my module, I have employed > spin locks both in process context using spin_lock() and spin_unlock() > APIs, as well as in ISR context using spin_lock_irqsave() and > spin_unlock_irqrestore() APIs. > > Here is a brief overview of how I have implemented spin locks in my module: > I certainly dont know whether the above and below are legal. Id be comparing my usage to working examples from the source-code. and you didnt say anything about your module or what it does. (fwiw, you'd get more help if it were "our" module, ie gpl'd) > However, during testing, I have encountered a scenario where a hard > LOCKUP (NMI watchdog: Watchdog detected hard LOCKUP on cpu 2) error > occurs, specifically when a process context code execution triggers > the spin_lock() function and is preempted by an interrupt that enters > the ISR context and encounters the spin_lock_irqsave() function. This > situation leads to the CPU being stuck indefinitely. > Id build w/o watchdog, to see what else goes wrong. 2 different errors might help find common cause. > My primary concern is to understand the appropriate usage of spin > locks in both process and ISR contexts to avoid such hard LOCKUP > errors. I am seeking clarification on the following points: > Documentation/locking/hwspinlock.rst > Is it safe to use spin_lock_irqsave() and spin_unlock_irqrestore() > APIs in ISR context and spin_lock() and spin_unlock() APIs in process > context simultaneously? > In scenarios where a process context code execution is preempted > by an interrupt and enters ISR context, how should spin locks be used > to prevent hard LOCKUP errors? > Are there any specific guidelines or best practices for using spin > locks in scenarios involving both process and ISR contexts? > > I would greatly appreciate any insights, guidance, or suggestions from > the experienced members of the Linux kernel community to help address > this issue and ensure the correct and efficient usage of spin locks in > my kernel module. > > Thank you very much for your time and assistance. > > -- > Thanks, > Sekhar > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@xxxxxxxxxxxxxxxxx > https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
