On 24/06/14 17:22, Nicolas Pitre wrote: > On Tue, 24 Jun 2014, Daniel Thompson wrote: > >> From: Anton Vorontsov <anton.vorontsov@xxxxxxxxxx> >> >> The FIQ debugger may be used to debug situations when the kernel stuck >> in uninterruptable sections, e.g. the kernel infinitely loops or >> deadlocked in an interrupt or with interrupts disabled. >> >> By default KGDB FIQ is disabled in runtime, but can be enabled with >> kgdb_fiq.enable=1 kernel command line option. >> >> Signed-off-by: Anton Vorontsov <anton.vorontsov@xxxxxxxxxx> >> Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx> >> Signed-off-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx> >> Cc: Russell King <linux@xxxxxxxxxxxxxxxx> >> Cc: Ben Dooks <ben.dooks@xxxxxxxxxxxxxxx> >> Cc: Dave Martin <Dave.Martin@xxxxxxx> >> --- >> arch/arm/Kconfig | 2 + >> arch/arm/Kconfig.debug | 18 ++++++ >> arch/arm/include/asm/kgdb.h | 7 +++ >> arch/arm/kernel/Makefile | 1 + >> arch/arm/kernel/kgdb_fiq.c | 124 +++++++++++++++++++++++++++++++++++++++ >> arch/arm/kernel/kgdb_fiq_entry.S | 87 +++++++++++++++++++++++++++ >> 6 files changed, 239 insertions(+) >> create mode 100644 arch/arm/kernel/kgdb_fiq.c >> create mode 100644 arch/arm/kernel/kgdb_fiq_entry.S > > [...] > >> +static long kgdb_fiq_setup_stack(void *info) >> +{ >> + struct pt_regs regs; >> + >> + regs.ARM_sp = __get_free_pages(GFP_KERNEL, THREAD_SIZE_ORDER) + >> + THREAD_START_SP; >> + WARN_ON(!regs.ARM_sp); > > Isn't this rather fatal if you can't allocate any stack? Why not using > BUG_ON(), or better yet propagate a proper error code back? Thanks for raising this. I think we can get rid of the allocation altogether. This stack is *way* oversized (it only needs to be 12 bytes). >> + >> + set_fiq_regs(®s); >> + return 0; >> +} >> + >> +/** >> + * kgdb_fiq_enable_nmi - Manage NMI-triggered entry to KGDB >> + * @on: Flag to either enable or disable an NMI >> + * >> + * This function manages NMIs that usually cause KGDB to enter. That is, not >> + * all NMIs should be enabled or disabled, but only those that issue >> + * kgdb_handle_exception(). >> + * >> + * The call counts disable requests, and thus allows to nest disables. But >> + * trying to enable already enabled NMI is an error. >> + */ >> +static void kgdb_fiq_enable_nmi(bool on) >> +{ >> + static atomic_t cnt; >> + int ret; >> + >> + ret = atomic_add_return(on ? 1 : -1, &cnt); >> + if (ret > 1 && on) { >> + /* >> + * There should be only one instance that calls this function >> + * in "enable, disable" order. All other users must call >> + * disable first, then enable. If not, something is wrong. >> + */ >> + WARN_ON(1); >> + return; >> + } > > Minor style suggestion: > > /* > * There should be only one instance that calls this function > * in "enable, disable" order. All other users must call > * disable first, then enable. If not, something is wrong. > */ > if (WARN_ON(ret > 1 && on)) > return; Will adopt this style. > Other than that... > > Acked-by: Nicolas Pitre <nico@xxxxxxxxxx> Thanks for review. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/