Hi all, With this support kernel can save functions call chain log into a persistent ram buffer that can be decoded and dumped after reboot through pstore filesystem. It can be used to determine what function was last called before a hang or an unexpected reset (caused by, for example, a buggy driver that abuses HW). Here's a "nano howto", to get the idea: # mount -t debugfs debugfs /sys/kernel/debug/ # cd /sys/kernel/debug/tracing # echo persistent > current_tracer # reboot -f [...] # mount -t pstore pstore /mnt/ # tail /mnt/ftrace-ramoops 0 ffffffff8101ea64 ffffffff8101bcda native_apic_mem_read <- disconnect_bsp_APIC+0x6a/0xc0 0 ffffffff8101ea44 ffffffff8101bcf6 native_apic_mem_write <- disconnect_bsp_APIC+0x86/0xc0 0 ffffffff81020084 ffffffff8101a4b5 hpet_disable <- native_machine_shutdown+0x75/0x90 0 ffffffff81005f94 ffffffff8101a4bb iommu_shutdown_noop <- native_machine_shutdown+0x7b/0x90 0 ffffffff8101a6a1 ffffffff8101a437 native_machine_emergency_restart <- native_machine_restart+0x37/0x40 0 ffffffff811f9876 ffffffff8101a73a acpi_reboot <- native_machine_emergency_restart+0xaa/0x1e0 0 ffffffff8101a514 ffffffff8101a772 mach_reboot_fixups <- native_machine_emergency_restart+0xe2/0x1e0 0 ffffffff811d9c54 ffffffff8101a7a0 __const_udelay <- native_machine_emergency_restart+0x110/0x1e0 0 ffffffff811d9c34 ffffffff811d9c80 __delay <- __const_udelay+0x30/0x40 0 ffffffff811d9d14 ffffffff811d9c3f delay_tsc <- __delay+0xf/0x20 Mostly the code comes from trace_persistent.c driver found in the Android git tree, written by Colin Cross <ccross@xxxxxxxxxxx> (according to sign-off history). I reworked the driver a little bit, and ported it to pstore subsystem. The patches depend on a pile of other pstore-related work, so if anyone is willing to try the patches, they would rather grab the whole git tree: git://git.infradead.org/users/cbou/linux-pstore.git or gitweb: http://git.infradead.org/users/cbou/linux-pstore.git Note that so far I've tried to not change the original idea, but if we consider inclusion, there are some open questions: 1. Should we merge persistent tracer with normal function tracer, i.e. add some flag that makes function tracer to duplicate the events into pstore (via a callback to pstore)? 2. If we keep the two separate, should the code live in fs/pstore or kernel/trace?.. I can see valid points for both approaches. Thanks, --- Documentation/ramoops.txt | 24 +++++++++ fs/pstore/Kconfig | 12 +++++ fs/pstore/Makefile | 6 +++ fs/pstore/ftrace.c | 122 ++++++++++++++++++++++++++++++++++++++++++++ fs/pstore/inode.c | 111 ++++++++++++++++++++++++++++++++++++++-- fs/pstore/internal.h | 49 ++++++++++++++++++ fs/pstore/platform.c | 13 ++++- fs/pstore/ram.c | 54 +++++++++++++++----- include/linux/pstore.h | 5 ++ include/linux/pstore_ram.h | 1 + kernel/trace/trace.c | 7 +-- 11 files changed, 384 insertions(+), 20 deletions(-) -- Anton Vorontsov Email: cbouatmailru@xxxxxxxxx _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
