On Fri, Aug 04, 2017 at 11:38:16AM +0100, James Morse wrote: > Hi Hoeun, > > On 04/08/17 08:02, Hoeun Ryu wrote: > > Commit 0ee5941 : (x86/panic: replace smp_send_stop() with kdump friendly > > version in panic path) introduced crash_smp_send_stop() which is a weak > > function and can be overriden by architecture codes to fix the side effect > > caused by commit f06e515 : (kernel/panic.c: add "crash_kexec_post_ > > notifiers" option). > > If I've understood correctly: if we boot with this option core code doesn't > use > our machine_crash_shutdown(), and instead calls crash_smp_send_stop(), which > we
No. Machine_crash_shutdown() is always called, but at that time, all the cpus other than the crashing cpu have already died in this case. > don't have, so it uses the default smp_send_stop(), which doesn't save the > regs. > > Thanks for catching this! > > > Could we rename smp_send_crash_stop() crash_smp_send_stop() and add the > called-twice logic there? They are similar enough that I'm getting them > muddled > already! > Nice. -Takahiro AKASHI > > Thanks, > > James > > > > ARM64 architecture uses the weak version function and the problem is that > > the weak function simply calls smp_send_stop() which makes other CPUs > > offline and takes away the chance to save crash information for nonpanic > > CPUs in machine_crash_shutdown() when crash_kexec_post_notifiers kernel > > option is enabled. > > > > Calling smp_send_crash_stop() in the function is useless because all > > nonpanic CPUs are already offline by smp_send_stop() in this case and > > smp_send_crash_stop() only works against online CPUs. > > > > The result is that /proc/vmcore is not available with the error messages; > > "Warning: Zero PT_NOTE entries found", "Kdump: vmcore not initialized". > > > > crash_smp_send_stop() is implemented for ARM64 architecture to fix this > > problem and the function (strong symbol version) saves crash information > > for nonpanic CPUs using smp_send_crash_stop() and machine_crash_shutdown() > > tries to save crash information for nonpanic CPUs only when > > crash_kexec_post_notifiers kernel option is disabled. > >
