powerpc: Fix smp_processor_id() in preemptible splat in set_breakpoint
Currently, on 8641D, which doesn't set CONFIG_HAVE_HW_BREAKPOINT
we get the following splat:
BUG: using smp_processor_id() in preemptible [00000000] code: login/1382
caller is set_breakpoint+0x1c/0xa0
CPU: 0 PID: 1382 Comm: login Not tainted 3.15.0-rc3-00041-g2aafe1a4d451 #1
Call Trace:
[decd5d80] [c0008dc4] show_stack+0x50/0x158 (unreliable)
[decd5dc0] [c03c6fa0] dump_stack+0x7c/0xdc
[decd5de0] [c01f8818] check_preemption_disabled+0xf4/0x104
[decd5e00] [c00086b8] set_breakpoint+0x1c/0xa0
[decd5e10] [c00d4530] flush_old_exec+0x2bc/0x588
[decd5e40] [c011c468] load_elf_binary+0x2ac/0x1164
[decd5ec0] [c00d35f8] search_binary_handler+0xc4/0x1f8
[decd5ef0] [c00d4ee8] do_execve+0x3d8/0x4b8
[decd5f40] [c001185c] ret_from_syscall+0x0/0x38
--- Exception: c01 at 0xfeee554
LR = 0xfeee7d4
The call path in this case is:
flush_thread
--> set_debug_reg_defaults
--> set_breakpoint
--> __get_cpu_var
Since preemption is enabled in the cleanup of flush thread, and
there is no need to disable it, introduce the distinction between
set_breakpoint and __set_breakpoint, leaving only the flush_thread
instance as the current user of set_breakpoint.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index f895a50..8a1edbe 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -496,7 +496,7 @@
return 0;
}
-void set_breakpoint(struct arch_hw_breakpoint *brk)
+void __set_breakpoint(struct arch_hw_breakpoint *brk)
{
__get_cpu_var(current_brk) = *brk;
@@ -506,6 +506,13 @@
set_dabr(brk);
}
+void set_breakpoint(struct arch_hw_breakpoint *brk)
+{
+ preempt_disable();
+ __set_breakpoint(brk);
+ preempt_enable();
+}
+
#ifdef CONFIG_PPC64
DEFINE_PER_CPU(struct cpu_usage, cpu_usage_array);
#endif
@@ -835,7 +842,7 @@
*/
#ifndef CONFIG_HAVE_HW_BREAKPOINT
if (unlikely(!hw_brk_match(&__get_cpu_var(current_brk), &new->thread.hw_brk)))
- set_breakpoint(&new->thread.hw_brk);
+ __set_breakpoint(&new->thread.hw_brk);
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
#endif