Hello.
Jason Wessel wrote:
> > -----Original Message-----
> > From: Sergei Shtylyov [mailto:[EMAIL PROTECTED]
> > >>>+
> > >>> if(!CHECK_EXCEPTION_STACK()) {
> >
> > Worth fixing if stmt style while at it. :-)
> >
> Noted and adjusted.
> Attached are the patches to be committed to core-lite.patch in the
> 2.6.21_uprev branch.
> Now that this is tested and confirmed to work, these will be committed
> with in the hour.
Looks like one of the patches could still use a bit cleanup -- sorry for
not noticing this yesterday... :-/
> Thanks,
> Jason.
> ------------------------------------------------------------------------
>
>
> Remove the breakpoint tasklet from the early initialization and defer
> breakpoints to the late_init.
>
> On SMP x86_64 in particular scheduling
> a tasklet too early can result in a silent death hang in the system,
> as there is a race to setup the exception stack vs the schduling
> context vs kgdb having the ability to debug the exception.
> Signed-off-by: Jason Wessel <[EMAIL PROTECTED]>
> ---
> kernel/kgdb.c | 15 ++++++++-------
> 1 file changed, 8 insertions(+), 7 deletions(-)
>
> Index: linux-2.6.21-standard/kernel/kgdb.c
> ===================================================================
> --- linux-2.6.21-standard.orig/kernel/kgdb.c
> +++ linux-2.6.21-standard/kernel/kgdb.c
> @@ -1670,7 +1670,7 @@ void kgdb_unregister_io_module(struct kg
> */
> static void kgdb_tasklet_bpt(unsigned long ing)
> {
> - if(CHECK_EXCEPTION_STACK())
> + if (CHECK_EXCEPTION_STACK())
> breakpoint();
> }
>
> @@ -1682,20 +1682,21 @@ DECLARE_TASKLET(kgdb_tasklet_breakpoint,
> */
> static void __init kgdb_early_entry(void)
> {
> + /* Let the architecture do any setup that it needs to. */
> + kgdb_arch_init();
> +
> /*
> * Don't try and do anything until the architecture is able to
> * setup the exception stack. In this case, it is up to the
> * architecture to hook in and look at us when they are ready.
> */
> - if(!CHECK_EXCEPTION_STACK()) {
> +
> + if (!CHECK_EXCEPTION_STACK()) {
> kgdb_initialized = -1;
> - tasklet_schedule(&kgdb_tasklet_breakpoint);
> + /* any kind of break point is deferred to late_init */
> return;
> }
>
> - /* Let the architecture do any setup that it needs to. */
> - kgdb_arch_init();
> -
> /* Now try the I/O. */
> /* For early entry kgdb_io_ops.init must be defined */
> if (!kgdb_io_ops.init || kgdb_io_ops.init()) {
> @@ -1879,7 +1880,7 @@ static int __init opt_kgdb_enter(char *s
> "gdb...\n");
> else {
> printk(KERN_CRIT "KGDB cannot initialize I/O yet.\n");
> - return;
> + return 0;
Hm, and how it compiled before?
> }
> }
> ------------------------------------------------------------------------
> This patch moves the early initialization code into a .init_text section
> vs having the possibility to call a function that has been deleted after
> the .init_text has been destroyed.
> In general this cannot happen but it does fix the compiler's concern about
> the possibility for it to happen.
> Signed-off-by: Jason Wessel <[EMAIL PROTECTED]>
> ---
> kernel/kgdb.c | 23 +++++++++++------------
> 1 file changed, 11 insertions(+), 12 deletions(-)
> Index: linux-2.6.21-standard/kernel/kgdb.c
> ===================================================================
> --- linux-2.6.21-standard.orig/kernel/kgdb.c
> +++ linux-2.6.21-standard/kernel/kgdb.c
> @@ -1788,17 +1788,6 @@ late_initcall(kgdb_late_entry);
> */
> void breakpoint(void)
> {
> - if (kgdb_initialized != 1) {
> - kgdb_early_entry();
> - if (kgdb_initialized == 1)
> - printk(KERN_CRIT "Waiting for connection from remote "
> - "gdb...\n");
> - else {
> - printk(KERN_CRIT "KGDB cannot initialize I/O yet.\n");
> - return;
> - }
> - }
> -
> atomic_set(&kgdb_setting_breakpoint, 1);
> wmb();
> BREAKPOINT();
> @@ -1883,7 +1872,17 @@ static int __init opt_kgdb_enter(char *s
> if (kgdb_initialized)
> return 0;
>
> - /* Call breakpoint() which will take care of init. */
> + if (kgdb_initialized != 1) {
Note that this check completely is superfluous here, i.e. the condition
would always be true after the first if stmt.
> + kgdb_early_entry();
> + if (kgdb_initialized == 1)
> + printk(KERN_CRIT "Waiting for connection from remote "
> + "gdb...\n");
> + else {
> + printk(KERN_CRIT "KGDB cannot initialize I/O yet.\n");
> + return;
> + }
> + }
> +
> breakpoint();
>
> return 0;
WBR, Sergei
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