> Do you think you can try the patch below?
<snip>
> --- a/kernel/kgdb.c
> +++ b/kernel/kgdb.c
> @@ -580,14 +580,13 @@ static void kgdb_wait(struct pt_regs *re
> * Make sure the above info reaches the primary CPU before
> * our cpu_in_kgdb[] flag setting does:
> */
> - smp_wmb();
> - atomic_set(&cpu_in_kgdb[cpu], 1);
> + atomic_inc(&cpu_in_kgdb[cpu]);
>
> /* Disable any cpu specific hw breakpoints */
> kgdb_disable_hw_debug(regs);
>
> /* Wait till primary CPU is done with debugging */
> - while (atomic_read(&passive_cpu_wait[cpu]))
> + while (atomic_add_return(0, &passive_cpu_wait[cpu]))
> cpu_relax();
>
> kgdb_info[cpu].debuggerinfo = NULL;
> @@ -598,7 +597,7 @@ static void kgdb_wait(struct pt_regs *re
> arch_kgdb_ops.correct_hw_break();
>
> /* Signal the primary CPU that we are done: */
> - atomic_set(&cpu_in_kgdb[cpu], 0);
> + atomic_dec(&cpu_in_kgdb[cpu]);
> touch_softlockup_watchdog_sync();
> clocksource_touch_watchdog();
> local_irq_restore(flags);
> @@ -1493,7 +1492,7 @@ acquirelock:
> * spin_lock code is good enough as a barrier so we don't
> * need one here:
> */
> - atomic_set(&cpu_in_kgdb[ks->cpu], 1);
> + atomic_inc(&cpu_in_kgdb[ks->cpu]);
>
> #ifdef CONFIG_SMP
> /* Signal the other CPUs to enter kgdb_wait() */
> @@ -1505,7 +1504,7 @@ acquirelock:
> * Wait for the other CPUs to be notified and be waiting for us:
> */
> for_each_online_cpu(i) {
> - while (!atomic_read(&cpu_in_kgdb[i]))
> + while (!atomic_add_return(0, &cpu_in_kgdb[i]))
> cpu_relax();
> }
>
> @@ -1528,7 +1527,7 @@ acquirelock:
>
> kgdb_info[ks->cpu].debuggerinfo = NULL;
> kgdb_info[ks->cpu].task = NULL;
> - atomic_set(&cpu_in_kgdb[ks->cpu], 0);
> + atomic_dec(&cpu_in_kgdb[ks->cpu]);
>
> if (!kgdb_single_step) {
> for (i = NR_CPUS-1; i >= 0; i--)
> @@ -1538,7 +1537,7 @@ acquirelock:
> * from the debugger.
> */
> for_each_online_cpu(i) {
> - while (atomic_read(&cpu_in_kgdb[i]))
> + while (atomic_add_return(0, &cpu_in_kgdb[i]))
> cpu_relax();
> }
> }
> @@ -1742,11 +1741,11 @@ EXPORT_SYMBOL_GPL(kgdb_unregister_io_mod
> */
> void kgdb_breakpoint(void)
> {
> - atomic_set(&kgdb_setting_breakpoint, 1);
> + atomic_inc(&kgdb_setting_breakpoint);
> wmb(); /* Sync point before breakpoint */
> arch_kgdb_breakpoint();
> wmb(); /* Sync point after breakpoint */
> - atomic_set(&kgdb_setting_breakpoint, 0);
> + atomic_dec(&kgdb_setting_breakpoint);
> }
> EXPORT_SYMBOL_GPL(kgdb_breakpoint);
Appears to work, but it's hard to be 100% with these sorts of things.
I ran the basic testsuite, the fork tests and the breakpoint tests as mentioned
in drivers/misc/kgdbts.c. The patch might introduce more barriers than we really
need, but this isn't performance-critical code and without it, KGDB is broken,
so:
Tested-by: Will Deacon <[email protected]>
Cheers,
Will
------------------------------------------------------------------------------
Download Intel® Parallel Studio Eval
Try the new software tools for yourself. Speed compiling, find bugs
proactively, and fine-tune applications for parallel performance.
See why Intel Parallel Studio got high marks during beta.
http://p.sf.net/sfu/intel-sw-dev
_______________________________________________
Kgdb-bugreport mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/kgdb-bugreport
