Fengguang Wu wrote: > On Thu, Sep 27, 2007 at 02:22:20AM -0700, Andrew Morton wrote: >> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.23-rc8/2.6.23-rc8-mm2/ > > Laurent, > > It triggered a WARNING on first run in qemu: Thank you to report it. > > [ 0.310000] WARNING: at arch/x86_64/kernel/smp.c:397 smp_call_function_mask() > [ 0.310000] > [ 0.310000] Call Trace: > [ 0.310000] [<ffffffff8100dbde>] dump_trace+0x3ee/0x4a0 > [ 0.310000] [<ffffffff8100dcd3>] show_trace+0x43/0x70 > [ 0.310000] [<ffffffff8100dd15>] dump_stack+0x15/0x20 > [ 0.310000] [<ffffffff8101cd44>] smp_call_function_mask+0x94/0xa0 > [ 0.310000] [<ffffffff8101cd69>] smp_call_function+0x19/0x20 > [ 0.310000] [<ffffffff8104277f>] on_each_cpu+0x1f/0x50 > [ 0.310000] [<ffffffff81026eac>] global_flush_tlb+0x8c/0x110 > [ 0.310000] [<ffffffff81025c85>] free_init_pages+0xe5/0xf0 > [ 0.310000] [<ffffffff81549b5e>] alternative_instructions+0x7e/0x150 > [ 0.310000] [<ffffffff8154a2ea>] check_bugs+0x1a/0x20 > [ 0.310000] [<ffffffff81540c4a>] start_kernel+0x2da/0x380 > [ 0.310000] [<ffffffff81540132>] _sinittext+0x132/0x140 the reason is the WARN_ON(): 390 int smp_call_function_mask(cpumask_t mask, 391 void (*func)(void *), void *info, 392 int wait) 393 { 394 int ret; 395 396 /* Can deadlock when called with interrupts disabled */ 397 WARN_ON(irqs_disabled()); 398 399 spin_lock(&call_lock); 400 ret = __smp_call_function_mask(mask, func, info, wait); 401 spin_unlock(&call_lock); 402 return ret; 403 } The patch I sent to Andi didn't include this WARN_ON() and it's why I didn't find this issue. (see http://lkml.org/lkml/2007/8/24/101) smp_call_function_mask() is called by smp_call_function() which calls a function on all CPU except current. The comment of smp_call_function() specifies: ... * You must not call this function with disabled interrupts or from a * hardware interrupt handler or from a bottom half handler. * Actually there are a few legal cases, like panic. */ So this WARN_ON() is correct, and the caller (global_flush_tlb()) doesn't follow this rule. I guess this WARN_ON() is only needed when we have current CPU in provided mask. So I think we should change: int smp_call_function (void (*func) (void *info), void *info, int nonatomic, int wait) { return smp_call_function_mask(cpu_online_map, func, info, wait); } ("cpu_online_map" is a bad choice, comment also specifies: "run a function on all other CPU") to int smp_call_function (void (*func) (void *info), void *info, int nonatomic, int wait) { int ret; cpumask_t allbutself; allbutself = cpu_online_map; cpu_clear(smp_processor_id(), allbutself); spin_lock(&call_lock); ret = __smp_call_function_mask(allbutself, func, info, wait); spin_unlock(&call_lock); return ret; } (which is smp_call_function_mask() without the WARN_ON() and without current cpu in the mask) Andi, is this correct ? Andrew, should I send a patch implementing this change ? Regards, Laurent -- ------------- [email protected] -------------- "Software is hard" - Donald Knuth
Attachment:
signature.asc
Description: OpenPGP digital signature
- Follow-Ups:
- Re: WARNING: at arch/x86_64/kernel/smp.c:397 smp_call_function_mask()
- From: Andrew Morton <[email protected]>
- Re: WARNING: at arch/x86_64/kernel/smp.c:397 smp_call_function_mask()
- References:
- 2.6.23-rc8-mm2
- From: Andrew Morton <[email protected]>
- WARNING: at arch/x86_64/kernel/smp.c:397 smp_call_function_mask()
- From: Fengguang Wu <[email protected]>
- 2.6.23-rc8-mm2
- Prev by Date: Re: [PATCH][resend] fix IDE legacy mode resources
- Next by Date: Re: [PATCH] spin_lock_unlocked cleanups
- Previous by thread: WARNING: at arch/x86_64/kernel/smp.c:397 smp_call_function_mask()
- Next by thread: Re: WARNING: at arch/x86_64/kernel/smp.c:397 smp_call_function_mask()
- Index(es):
 |