Martin Wilck <martin.wilck at fujitsu-siemens.com> writes: > Vivek Goyal wrote: > >> Got this oops while testing your patch when I did >> "echo c > /proc/sysrq-trigger" > > That's bad :-( > > ... >> Unable to handle kernel NULL pointer dereference at 0000000000000000 RIP: > [<0000000000000000>] >> <IRQ> [<ffffffff8025afd0>] handle_edge_irq+0x5c/0x127 >> [<ffffffff8020e1ae>] do_IRQ+0xf1/0x15f >> [<ffffffff8020c191>] ret_from_intr+0x0/0xa >> <EOI> <NMI> [<ffffffff80351ae3>] __delay+0x6/0x10 >> [<ffffffff8021e328>] crash_nmi_callback+0x4b/0x77 > > Obviously, it the oops occurs after the IRQs are re-enabled in > crash_nmi_callback(). > It appears that desc->chip->mask (in mask_ack_irq(), kernel/irq/chip.c:462) was > NULL. > I have no idea how my patch could cause that. > > This proves that re-enabling IRQs in this situation is too dangerous :-(. > I really did hundreds of dumps in different ways (echo c>/proc/sysrq-trigger, > forcing Oops and panic(), actually hititng Alt-Sysrq) and this never happened to > me. This reminds me. There is currently an issue that no has finished converting the lapic to the new generic irq way. Which can have this effect. Eric
