In message <20010723162909.D822@athlon.random> you write:
> > Why not fix all the cases? Why have this wierd secret rule that
> > cpu_raise_softirq() should not be called with irqs disabled?
>
> cpu_raise_softirq _can_ be called with irq disabled too just now, irq
> enabled or disabled has no influence at all on cpu_raise_softirq.
No, you are wrong. If I do (NOT in a hw interrupt handler):
local_irq_save(flags);
...
cpu_raise_softirq(smp_processor_id(), FOO_SOFTIRQ);
...
local_irq_restore(flags);
ksoftirqd won't get woken, and the FOO soft irq won't get run until
the next interrupt comes in. You solved (horribly) the analagous case
for local_bh_disable/enable, but not this one.
Below as suggested in my previous email (x86 only, untested). I also
added a couple of comments. There's still the issue of stack
overflows if you get hit hard enough with interrupts (do_softirq is
exposed to reentry for short periods), but that's separate.
Linus, please consider,
Rusty.
-- Premature optmztion is rt of all evl. --DKdiff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.4.7-official/arch/i386/kernel/irq.c working-2.4.7-unclean/arch/i386/kernel/irq.c --- linux-2.4.7-official/arch/i386/kernel/irq.c Sat Jul 7 07:48:47 2001 +++ working-2.4.7-unclean/arch/i386/kernel/irq.c Tue Jul 24 17:29:19 2001 @@ -576,6 +576,7 @@ unsigned int status; kstat.irqs[cpu][irq]++; + in_hw_irq(cpu) = 1; spin_lock(&desc->lock); desc->handler->ack(irq); /* @@ -633,6 +634,7 @@ */ desc->handler->end(irq); spin_unlock(&desc->lock); + in_hw_irq(cpu) = 0; if (softirq_pending(cpu)) do_softirq(); diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.4.7-official/include/asm-i386/hardirq.h working-2.4.7-unclean/include/asm-i386/hardirq.h --- linux-2.4.7-official/include/asm-i386/hardirq.h Sun Jul 22 13:13:21 2001 +++ working-2.4.7-unclean/include/asm-i386/hardirq.h Tue Jul 24 18:40:09 2001 @@ -13,6 +13,7 @@ unsigned int __syscall_count; struct task_struct * __ksoftirqd_task; /* waitqueue is too large */ unsigned int __nmi_count; /* arch dependent */ + int __in_hw_irq; } ____cacheline_aligned irq_cpustat_t; #include <linux/irq_cpustat.h> /* Standard mappings for irq_cpustat_t above */ diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.4.7-official/include/asm-i386/softirq.h working-2.4.7-unclean/include/asm-i386/softirq.h --- linux-2.4.7-official/include/asm-i386/softirq.h Sun Jul 22 13:13:21 2001 +++ working-2.4.7-unclean/include/asm-i386/softirq.h Tue Jul 24 19:07:24 2001 @@ -4,46 +4,15 @@ #include <asm/atomic.h> #include <asm/hardirq.h> -#define __cpu_bh_enable(cpu) \ +#define cpu_bh_enable(cpu) \ do { barrier(); local_bh_count(cpu)--; } while (0) #define cpu_bh_disable(cpu) \ do { local_bh_count(cpu)++; barrier(); } while (0) #define local_bh_disable() cpu_bh_disable(smp_processor_id()) -#define __local_bh_enable() __cpu_bh_enable(smp_processor_id()) +#define local_bh_enable() cpu_bh_enable(smp_processor_id()) #define in_softirq() (local_bh_count(smp_processor_id()) != 0) - -/* - * NOTE: this assembly code assumes: - * - * (char *)&local_bh_count - 8 == (char *)&softirq_pending - * - * If you change the offsets in irq_stat then you have to - * update this code as well. - */ -#define local_bh_enable() \ -do { \ - unsigned int *ptr = &local_bh_count(smp_processor_id()); \ - \ - barrier(); \ - if (!--*ptr) \ - __asm__ __volatile__ ( \ - "cmpl $0, -8(%0);" \ - "jnz 2f;" \ - "1:;" \ - \ - ".section .text.lock,\"ax\";" \ - "2: pushl %%eax; pushl %%ecx; pushl %%edx;" \ - "call %c1;" \ - "popl %%edx; popl %%ecx; popl %%eax;" \ - "jmp 1b;" \ - ".previous;" \ - \ - : /* no output */ \ - : "r" (ptr), "i" (do_softirq) \ - /* no registers clobbered */ ); \ -} while (0) #define __cpu_raise_softirq(cpu, nr) __set_bit(nr, &softirq_pending(cpu)) diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.4.7-official/include/linux/irq_cpustat.h working-2.4.7-unclean/include/linux/irq_cpustat.h --- linux-2.4.7-official/include/linux/irq_cpustat.h Sun Jul 22 13:13:24 2001 +++ working-2.4.7-unclean/include/linux/irq_cpustat.h Tue Jul 24 18:40:09 2001 @@ -31,6 +31,7 @@ #define local_bh_count(cpu) __IRQ_STAT((cpu), __local_bh_count) #define syscall_count(cpu) __IRQ_STAT((cpu), __syscall_count) #define ksoftirqd_task(cpu) __IRQ_STAT((cpu), __ksoftirqd_task) +#define in_hw_irq(cpu) __IRQ_STAT((cpu), __in_hw_irq) /* arch dependent irq_stat fields */ #define nmi_count(cpu) __IRQ_STAT((cpu), __nmi_count) /* i386, ia64 */ diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.4.7-official/kernel/softirq.c working-2.4.7-unclean/kernel/softirq.c --- linux-2.4.7-official/kernel/softirq.c Sun Jul 22 13:13:25 2001 +++ working-2.4.7-unclean/kernel/softirq.c Tue Jul 24 19:26:03 2001 @@ -68,6 +68,7 @@ long flags; __u32 mask; + /* Prevent reentry: we always hold an irq or bh count */ if (in_interrupt()) return; @@ -102,8 +103,10 @@ mask &= ~pending; goto restart; } - __local_bh_enable(); + local_bh_enable(); + /* More came in while we were processing? Let + softirqd handle the overload. */ if (pending) wakeup_softirqd(cpu); } @@ -115,16 +118,10 @@ { __cpu_raise_softirq(cpu, nr); - /* - * If we're in an interrupt or bh, we're done - * (this also catches bh-disabled code). We will - * actually run the softirq once we return from - * the irq or bh. - * - * Otherwise we wake up ksoftirqd to make sure we - * schedule the softirq soon. - */ - if (!(local_irq_count(cpu) | local_bh_count(cpu))) + /* If we're in an interrupt handler, then softirqs get + processed on the way out. For all other (rarer) cases, + wake softirqd to deal with it soon. */ + if (!in_hw_irq(cpu)) wakeup_softirqd(cpu); } - 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/
This archive was generated by hypermail 2b29 : Tue Jul 31 2001 - 21:00:15 EST