powerpc: Fix smp_processor_id() in preemptible splat in set_breakpoint
authorPaul Gortmaker <paul.gortmaker@windriver.com>
Tue, 29 Apr 2014 19:25:17 +0000 (15:25 -0400)
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>
Tue, 20 May 2014 00:54:06 +0000 (10:54 +1000)
commit21f585073d6347651f2262da187606fa1c4ee16d
tree5ec5947a36e0a7e7fe458d13523d4036cc748ff1
parent04c32a516806ec74b62048baf4cddcbb840927db
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>
arch/powerpc/include/asm/debug.h
arch/powerpc/include/asm/hw_breakpoint.h
arch/powerpc/kernel/hw_breakpoint.c
arch/powerpc/kernel/process.c
arch/powerpc/kernel/signal.c
arch/powerpc/xmon/xmon.c