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Paul Burton 6b8322576e MIPS: Force CPUs to lose FP context during mode switches 
Commit 9791554b45 ("MIPS,prctl: add PR_[GS]ET_FP_MODE prctl options
for MIPS") added support for the PR_SET_FP_MODE prctl, which allows a
userland program to modify its FP mode at runtime. This is most notably
required if dynamic linking leads to the FP mode requirement changing at
runtime from that indicated in the initial executable's ELF header. In
order to avoid overhead in the general FP context restore code, it aimed
to have threads in the process become unable to enable the FPU during a
mode switch & have the thread calling the prctl syscall wait for all
other threads in the process to be context switched at least once. Once
that happens we can know that no thread in the process whose mode will
be switched has live FP context, and it's safe to perform the mode
switch. However in the (rare) case of modeswitches occurring in
multithreaded programs this can lead to indeterminate delays for the
thread invoking the prctl syscall, and the code monitoring for those
context switches was woefully inadequate for all but the simplest cases.

Fix this by broadcasting an IPI if other CPUs may have live FP context
for an affected thread, with a handler causing those CPUs to relinquish
their FPU ownership. Threads will then be allowed to continue running
but will stall on the wait_on_atomic_t in enable_restore_fp_context if
they attempt to use FP again whilst the mode switch is still in
progress. The end result is less fragile poking at scheduler context
switch counts & a more expedient completion of the mode switch.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Fixes: 9791554b45 ("MIPS,prctl: add PR_[GS]ET_FP_MODE prctl options for MIPS")
Reviewed-by: Maciej W. Rozycki <macro@imgtec.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: stable <stable@vger.kernel.org> # v4.0+
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13145/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
 		2016-05-13 15:30:25 +02:00
..
.gitignore
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8250-platform.c mips: remove needless include of module.h from core kernel files. 2011-10-31 19:30:57 -04:00
Makefile MIPS: Kernel: Add relocate.c 2016-05-13 14:02:02 +02:00
asm-offsets.c MIPS: Support extended ASIDs 2016-05-13 14:02:20 +02:00
binfmt_elfn32.c MIPS: ELF: Unify ABI classification macros 2016-05-13 15:30:25 +02:00
binfmt_elfo32.c MIPS: ELF: Unify ABI classification macros 2016-05-13 15:30:25 +02:00
bmips_5xxx_init.S MIPS: BMIPS: Make whitespacely correct. 2016-05-09 12:00:01 +02:00
bmips_vec.S MIPS: BMIPS: Add Whirlwind (BMIPS5200) initialization code 2016-05-09 12:00:01 +02:00
branch.c MIPS: Fix BC1{EQ,NE}Z return offset calculation 2016-05-13 14:02:21 +02:00
cevt-bcm1480.c MIPS: cevt-bcm1480: Migrate to new 'set-state' interface 2015-09-03 12:07:51 +02:00
cevt-ds1287.c MIPS: cevt-ds1287: Migrate to new 'set-state' interface 2015-09-03 12:07:51 +02:00
cevt-gt641xx.c MIPS: cevt-gt641xx: Migrate to new 'set-state' interface 2015-09-03 12:07:51 +02:00
cevt-r4k.c MIPS: cevt-r4k: Migrate to new 'set-state' interface 2015-09-03 12:07:52 +02:00
cevt-sb1250.c MIPS: cevt-sb1250: Migrate to new 'set-state' interface 2015-09-03 12:07:52 +02:00
cevt-txx9.c MIPS: cevt-txx9: Migrate to new 'set-state' interface 2015-09-03 12:07:53 +02:00
cps-vec-ns16550.S MIPS: CPS: Early debug using an ns16550-compatible UART 2015-11-11 08:34:25 +01:00
cps-vec.S MIPS: smp-cps: Stop printing EJTAG exceptions to UART 2016-05-13 14:01:51 +02:00
cpu-bugs64.c MIPS: Use EXCCODE_ constants with set_except_vector() 2016-01-24 03:28:21 +01:00
cpu-probe.c MIPS: Add probing & defs for VZ & guest features 2016-05-13 15:30:25 +02:00
crash.c MIPS: Fix crash registers on non-crashing CPUs 2016-05-09 12:00:00 +02:00
crash_dump.c mips: Convert pr_warning to pr_warn 2014-11-24 07:44:51 +01:00
csrc-bcm1480.c MIPS: csrc-bcm1480: Implement read_sched_clock 2015-04-01 17:21:27 +02:00
csrc-ioasic.c MIPS: csrc-ioasic: Implement read_sched_clock 2015-04-01 17:21:28 +02:00
csrc-r4k.c MIPS: VDSO: Add implementations of gettimeofday() and clock_gettime() 2015-11-11 08:36:41 +01:00
csrc-sb1250.c MIPS: csrc-sb1250: Implement read_sched_clock 2015-04-01 17:21:33 +02:00
early_printk.c early_printk: consolidate random copies of identical code 2013-04-29 18:28:13 -07:00
early_printk_8250.c MIPS: Add 8250/16550 serial early printk driver 2013-10-29 21:24:36 +01:00
elf.c MIPS: Add IEEE Std 754 conformance mode selection 2016-01-20 00:39:20 +01:00
entry.S MIPS: kernel: entry.S: Set correct ISA level for mips_ihb 2015-04-10 15:41:46 +02:00
ftrace.c Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2014-08-07 08:47:00 -07:00
genex.S MIPS: genex: Indent delay slots & clean whitespace 2016-05-13 14:02:20 +02:00
gpio_txx9.c MIPS: txx9: switch to gpiochip_add_data() 2016-02-19 09:51:44 +01:00
head.S MIPS: Remove redundant asm/pgtable-bits.h inclusions 2016-05-13 15:30:25 +02:00
i8253.c MIPS: irq: Remove IRQF_DISABLED 2011-12-07 22:03:45 +00:00
idle.c MIPS: Loongson: Add Loongson-3A R2 basic support 2016-05-13 14:02:14 +02:00
irq-gt641xx.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
irq-msc01.c MIPS: MSC: Prevent out-of-bounds writes to MIPS SC ioremap'd region 2014-06-26 10:48:23 +01:00
irq-rm7000.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
irq.c MIPS: IRQ/IP27: Move IRQ allocation API to platform code. 2015-06-21 21:54:31 +02:00
irq_txx9.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
jump_label.c jump_label: Rename JUMP_LABEL_{EN,DIS}ABLE to JUMP_LABEL_{JMP,NOP} 2015-08-03 11:34:12 +02:00
kgdb.c MIPS: Get rid of 'kgdb_early_setup' cruft. 2015-06-21 21:54:10 +02:00
kprobes.c mips: Replace __get_cpu_var uses 2014-08-26 13:45:51 -04:00
linux32.c unify compat fanotify_mark(2), switch to COMPAT_SYSCALL_DEFINE 2013-05-09 13:46:38 -04:00
machine_kexec.c MIPS: kdump: Set correct value to kexec_indirection_page variable 2014-08-25 16:33:44 +02:00
mcount.S MIPS: mcount: Adjust stack pointer for static trace in MIPS32 2014-09-26 11:41:17 +02:00
mips-cm.c MIPS: Fix misspellings in comments. 2016-04-03 12:32:09 +02:00
mips-cpc.c MIPS: CM, CPC: Ensure core-other GCRs reflect the correct core 2015-11-11 08:35:18 +01:00
mips-mt-fpaff.c MIPS: Fix sched_getaffinity with MT FPAFF enabled 2015-08-03 09:25:02 +02:00
mips-mt.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
mips-r2-to-r6-emul.c MIPS64: R6: R2 emulation bugfix 2016-05-09 12:00:04 +02:00
mips_ksyms.c MIPS: uaccess: Take EVA into account in [__]clear_user 2015-12-22 11:58:43 +01:00
mips_machine.c MIPS: move mips_{set,get}_machine_name() to a more generic place 2013-05-08 01:19:07 +02:00
module-rela.c MIPS: module: fix incorrect IS_ERR_VALUE macro usages 2016-05-13 14:02:11 +02:00
module.c MIPS: module: fix incorrect IS_ERR_VALUE macro usages 2016-05-13 14:02:11 +02:00
octeon_switch.S MIPS: Fix octeon FP context switch handling 2015-10-02 19:16:06 +02:00
perf_event.c MIPS: perf: Reorganize contents of perf support files. 2011-10-24 23:34:26 +01:00
perf_event_mipsxx.c MIPS: Add perf counter feature 2016-05-13 15:30:25 +02:00
pm-cps.c MIPS: pm-cps: Avoid offset overflow on MIPSr6 2016-05-13 14:01:48 +02:00
pm.c MIPS: Fix watchpoint restoration 2016-05-09 12:00:02 +02:00
proc.c MIPS: Detect DSP v3 support 2016-05-13 14:01:57 +02:00
process.c MIPS: Force CPUs to lose FP context during mode switches 2016-05-13 15:30:25 +02:00
prom.c MIPS: Fix build with CONFIG_OF=y for non OF-enabled targets 2015-08-03 09:25:00 +02:00
ptrace.c MIPS: ptrace: Prevent writes to read-only FCSR bits 2016-05-13 15:30:25 +02:00
ptrace32.c MIPS: Remove asm/user.h 2014-08-02 00:06:37 +02:00
r4k_fpu.S MIPS: Use copy_s.fmt rather than copy_u.fmt 2016-05-09 12:00:04 +02:00
r4k_switch.S MIPS: Remove redundant asm/pgtable-bits.h inclusions 2016-05-13 15:30:25 +02:00
r2300_fpu.S MIPS: Avoid variant of .type unsupported by LLVM Assembler 2016-02-29 11:23:49 +01:00
r2300_switch.S MIPS: Fix R2300 FP context switch handling 2015-10-02 19:16:46 +02:00
r6000_fpu.S MIPS: Fix build with binutils 2.24.51+ 2014-11-07 15:07:36 +01:00
relocate.c MIPS: Kernel: Implement KASLR using CONFIG_RELOCATABLE 2016-05-13 14:02:03 +02:00
relocate_kernel.S MIPS: Replace add and sub instructions in relocate_kernel.S with addiu 2015-08-03 15:26:30 +02:00
reset.c MIPS: Provide fallback reboot/poweroff/halt implementations 2015-04-01 17:21:58 +02:00
rtlx-cmp.c MIPS: APRP: Fix an issue when device_create() fails. 2014-08-01 17:30:35 +02:00
rtlx-mt.c MIPS: APRP: Fix an issue when device_create() fails. 2014-08-01 17:30:35 +02:00
rtlx.c MIPS: rtlx: Remove KERN_DEBUG from pr_debug() arguments in rtlx.c 2014-11-24 07:44:04 +01:00
scall32-o32.S MIPS: scall: Handle seccomp filters which redirect syscalls 2016-05-13 14:02:00 +02:00
scall64-64.S MIPS: scall: Handle seccomp filters which redirect syscalls 2016-05-13 14:02:00 +02:00
scall64-n32.S MIPS: scall: Handle seccomp filters which redirect syscalls 2016-05-13 14:02:00 +02:00
scall64-o32.S MIPS: scall: Handle seccomp filters which redirect syscalls 2016-05-13 14:02:00 +02:00
segment.c MIPS: Declare mips_debugfs_dir in a header 2015-10-26 09:49:42 +01:00
setup.c MIPS: Octeon: detect and fix byte swapped initramfs 2016-05-13 15:30:25 +02:00
signal-common.h MIPS: Save MSA extended context around signals 2015-09-03 12:07:59 +02:00
signal.c MIPS64: signal: Fix o32 sigaction syscall 2016-05-13 14:02:16 +02:00
signal32.c MIPS: Support sending SIG_SYS to 32bit userspace from 64bit kernel 2016-05-13 14:02:00 +02:00
signal_n32.c MIPS: Initial implementation of a VDSO 2015-11-11 08:36:36 +01:00
smp-bmips.c MIPS: BMIPS: Add early CPU initialization code 2016-05-13 14:01:55 +02:00
smp-cmp.c MIPS: Make smp CMP, CPS and MT use the new generic IPI functions 2016-02-25 10:56:58 +01:00
smp-cps.c MIPS: smp-cps: Add nothreads kernel parameter 2016-05-13 14:01:50 +02:00
smp-gic.c MIPS: CM: make use of mips_cm_{lock,unlock}_other 2015-11-11 08:35:17 +01:00
smp-mt.c MIPS: Make smp CMP, CPS and MT use the new generic IPI functions 2016-02-25 10:56:58 +01:00
smp-up.c MIPS: SMP: Remove plat_smp_ops cpus_done method. 2014-05-27 11:06:42 +02:00
smp.c MIPS: Don't BUG_ON when no IPI domain is found 2016-05-09 12:00:00 +02:00
spinlock_test.c MIPS: Declare mips_debugfs_dir in a header 2015-10-26 09:49:42 +01:00
spram.c MIPS: Add P6600 cases to CPU switch statements 2016-05-13 14:01:52 +02:00
stacktrace.c MIPS: Add LATENCYTOP support 2015-11-11 08:36:46 +01:00
sync-r4k.c MIPS: sync-r4k: reduce skew while synchronization 2016-01-24 01:31:51 +01:00
syscall.c MIPS: kernel: syscall: Set the appropriate ISA level for MIPS R6 2015-02-17 15:37:29 +00:00
sysrq.c MIPS: Refactor dumping of TLB registers for r3k/r4k 2015-09-03 12:07:45 +02:00
time.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
topology.c
…
traps.c MIPS: Retrieve ASID masks using function accepting struct cpuinfo_mips 2016-05-13 14:02:20 +02:00
unaligned.c MIPS: Allow emulation for unaligned [LS]DXC1 instructions 2016-05-13 15:30:25 +02:00
uprobes.c MIPS: Add uprobes support. 2015-09-03 12:08:05 +02:00
vdso.c MIPS: VDSO: Add implementations of gettimeofday() and clock_gettime() 2015-11-11 08:36:41 +01:00
vmlinux.lds.S MIPS: Reserve space for relocation table 2016-05-13 14:02:02 +02:00
vpe-cmp.c MIPS: APRP: Add VPE loader support for CMP platforms. 2014-01-22 20:19:02 +01:00
vpe-mt.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
vpe.c module: use a structure to encapsulate layout. 2015-12-04 22:46:25 +01:00
watch.c MIPS: Add and use watch register field definitions 2016-05-13 14:02:13 +02:00