https://github.com/torvalds/linux
Revision 9ef0f88fe5466c2ca1d2975549ba6be502c464c1 authored by John David Anglin on 07 March 2018, 13:18:05 UTC, committed by Helge Deller on 17 March 2018, 10:49:39 UTC
Just when I had decided that flush_cache_range() was always called with a valid context, Helge reported two cases where the "BUG_ON(!vma->vm_mm->context);" was hit on the phantom buildd: kernel BUG at /mnt/sdb6/linux/linux-4.15.4/arch/parisc/kernel/cache.c:587! CPU: 1 PID: 3254 Comm: kworker/1:2 Tainted: G D 4.15.0-1-parisc64-smp #1 Debian 4.15.4-1+b1 Workqueue: events free_ioctx IAOQ[0]: flush_cache_range+0x164/0x168 IAOQ[1]: flush_cache_page+0x0/0x1c8 RP(r2): unmap_page_range+0xae8/0xb88 Backtrace: [<00000000404a6980>] unmap_page_range+0xae8/0xb88 [<00000000404a6ae0>] unmap_single_vma+0xc0/0x188 [<00000000404a6cdc>] zap_page_range_single+0x134/0x1f8 [<00000000404a702c>] unmap_mapping_range+0x1cc/0x208 [<0000000040461518>] truncate_pagecache+0x98/0x108 [<0000000040461624>] truncate_setsize+0x9c/0xb8 [<00000000405d7f30>] put_aio_ring_file+0x80/0x100 [<00000000405d803c>] aio_free_ring+0x8c/0x290 [<00000000405d82c0>] free_ioctx+0x80/0x180 [<0000000040284e6c>] process_one_work+0x21c/0x668 [<00000000402854c4>] worker_thread+0x20c/0x778 [<0000000040291d44>] kthread+0x2d4/0x2e0 [<0000000040204020>] end_fault_vector+0x20/0xc0 This indicates that we need to handle the no context case in flush_cache_range() as we do in flush_cache_mm(). In thinking about this, I realized that we don't need to flush the TLB when there is no context. So, I added context checks to the large flush cases in flush_cache_mm() and flush_cache_range(). The large flush case occurs frequently in flush_cache_mm() and the change should improve fork performance. The v2 version of this change removes the BUG_ON from flush_cache_page() by skipping the TLB flush when there is no context. I also added code to flush the TLB in flush_cache_mm() and flush_cache_range() when we have a context that's not current. Now all three routines handle TLB flushes in a similar manner. Signed-off-by: John David Anglin <dave.anglin@bell.net> Cc: stable@vger.kernel.org # 4.9+ Signed-off-by: Helge Deller <deller@gmx.de>
1 parent 8f5fd92
Tip revision: 9ef0f88fe5466c2ca1d2975549ba6be502c464c1 authored by John David Anglin on 07 March 2018, 13:18:05 UTC
parisc: Handle case where flush_cache_range is called with no context
parisc: Handle case where flush_cache_range is called with no context
Tip revision: 9ef0f88
legacy_instructions.txt
The arm64 port of the Linux kernel provides infrastructure to support
emulation of instructions which have been deprecated, or obsoleted in
the architecture. The infrastructure code uses undefined instruction
hooks to support emulation. Where available it also allows turning on
the instruction execution in hardware.
The emulation mode can be controlled by writing to sysctl nodes
(/proc/sys/abi). The following explains the different execution
behaviours and the corresponding values of the sysctl nodes -
* Undef
Value: 0
Generates undefined instruction abort. Default for instructions that
have been obsoleted in the architecture, e.g., SWP
* Emulate
Value: 1
Uses software emulation. To aid migration of software, in this mode
usage of emulated instruction is traced as well as rate limited
warnings are issued. This is the default for deprecated
instructions, .e.g., CP15 barriers
* Hardware Execution
Value: 2
Although marked as deprecated, some implementations may support the
enabling/disabling of hardware support for the execution of these
instructions. Using hardware execution generally provides better
performance, but at the loss of ability to gather runtime statistics
about the use of the deprecated instructions.
The default mode depends on the status of the instruction in the
architecture. Deprecated instructions should default to emulation
while obsolete instructions must be undefined by default.
Note: Instruction emulation may not be possible in all cases. See
individual instruction notes for further information.
Supported legacy instructions
-----------------------------
* SWP{B}
Node: /proc/sys/abi/swp
Status: Obsolete
Default: Undef (0)
* CP15 Barriers
Node: /proc/sys/abi/cp15_barrier
Status: Deprecated
Default: Emulate (1)
* SETEND
Node: /proc/sys/abi/setend
Status: Deprecated
Default: Emulate (1)*
Note: All the cpus on the system must have mixed endian support at EL0
for this feature to be enabled. If a new CPU - which doesn't support mixed
endian - is hotplugged in after this feature has been enabled, there could
be unexpected results in the application.
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