Messages in this thread Patch in this message | | | Date | Fri, 2 Aug 2002 02:12:58 +0200 | From | Willy TARREAU <> | Subject | [PATCH] solved APM bug with -rc5 (take 2) |
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On Thu, Aug 01, 2002 at 11:16:23PM +0100, Alan Cox wrote: > On Thu, 2002-08-01 at 21:35, Willy TARREAU wrote: > > +#ifdef CONFIG_SMP > > + /* 2002/08/01 - WT > > + * This is to avoid random crashes at boot time during initialization > > + * on SMP systems in case of "apm=power-off" mode. Seen on ASUS A7M266D. > > + * Some bioses don't like being called from CPU != 0. > > + */ > > + while (cpu_number_map(smp_processor_id()) != 0) { > > + schedule(); > > + } > > +#endif > > What guarantees that loop will ever exit ?
I asked Ingo for some advice, and he gently sent me a piece of code as an example of how to reliably bind a task to a CPU. I tried it, and it's OK here. I could reliably switch several times from cpu0 to cpu1, then back to cpu0. Since it was cleaner than the previous method, I also did the same for apm_power_off(), thus getting rid of apm_magic() and its dedicated thread. Then again, I tested with multiple cpu switches, and every time, my system correctly handles the case. I'm writing this mail under 2.4.19-rc5.
So here is the patch against 2.4.19-rc5, hoping it will get in this time. I think it should apply without a glitch to 2.4.19-rc5-ac1, but don't know about 2.5, nor even if it is needed.
Feedback welcome, of course ;-)
Cheers, Willy
--- linux-2.4.19-rc5/arch/i386/kernel/apm.c Thu Aug 1 22:07:39 2002 +++ linux-2.4.19-rc5-fix/arch/i386/kernel/apm.c Fri Aug 2 01:52:55 2002 @@ -862,14 +862,6 @@ apm_do_busy(); } -#ifdef CONFIG_SMP -static int apm_magic(void * unused) -{ - while (1) - schedule(); -} -#endif - /** * apm_power_off - ask the BIOS to power off * @@ -897,10 +889,11 @@ */ #ifdef CONFIG_SMP /* Some bioses don't like being called from CPU != 0 */ - while (cpu_number_map(smp_processor_id()) != 0) { - kernel_thread(apm_magic, NULL, - CLONE_FS | CLONE_FILES | CLONE_SIGHAND | SIGCHLD); + if (cpu_number_map(smp_processor_id()) != 0) { + current->cpus_allowed = 1; schedule(); + if (unlikely(cpu_number_map(smp_processor_id()) != 0)) + BUG(); } #endif if (apm_info.realmode_power_off) @@ -1661,6 +1654,21 @@ strcpy(current->comm, "kapmd"); sigfillset(¤t->blocked); +#ifdef CONFIG_SMP + /* 2002/08/01 - WT + * This is to avoid random crashes at boot time during initialization + * on SMP systems in case of "apm=power-off" mode. Seen on ASUS A7M266D. + * Some bioses don't like being called from CPU != 0. + * Method suggested by Ingo Molnar. + */ + if (cpu_number_map(smp_processor_id()) != 0) { + current->cpus_allowed = 1; + schedule(); + if (unlikely(cpu_number_map(smp_processor_id()) != 0)) + BUG(); + } +#endif + if (apm_info.connection_version == 0) { apm_info.connection_version = apm_info.bios.version; if (apm_info.connection_version > 0x100) { @@ -1707,7 +1715,7 @@ } } - if (debug && (smp_num_cpus == 1)) { + if (debug) { error = apm_get_power_status(&bx, &cx, &dx); if (error) printk(KERN_INFO "apm: power status not available\n"); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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