From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
npiggin@gmail.com, msuchanek@suse.de
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: [PATCH v6 3/2] powerpc/syscall: Avoid storing 'current' in another pointer
Date: Wed, 10 Feb 2021 08:44:09 +0000 (UTC) [thread overview]
Message-ID: <ad0363ff0ff8c125f40e1cdc589a85bbd7e31693.1612946484.git.christophe.leroy@csgroup.eu> (raw)
In-Reply-To: <cover.1612898425.git.christophe.leroy@csgroup.eu>
By saving the pointer pointing to thread_info.flags, gcc copies r2
in a non-volatile register.
We know 'current' doesn't change, so avoid that intermediaite pointer.
Reduces null_syscall benchmark by 2 cycles (322 => 320 cycles)
On PPC64, gcc seems to know that 'current' is not changing, and it keeps
it in a non volatile register to avoid multiple read of 'current' in paca.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v5: Also in interrupt exit prepare
v6: Removed change related to booke current->thread.debug
v7: Rebased on top of "powerpc/32: Handle bookE debugging in C in syscall entry/exit"
---
arch/powerpc/kernel/interrupt.c | 21 +++++++++------------
1 file changed, 9 insertions(+), 12 deletions(-)
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index f93664ad4a5e..398cd86b6ada 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -241,7 +241,6 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
struct pt_regs *regs,
long scv)
{
- unsigned long *ti_flagsp = ¤t_thread_info()->flags;
unsigned long ti_flags;
unsigned long ret = 0;
bool is_not_scv = !IS_ENABLED(CONFIG_PPC_BOOK3S_64) || !scv;
@@ -257,7 +256,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
/* Check whether the syscall is issued inside a restartable sequence */
rseq_syscall(regs);
- ti_flags = *ti_flagsp;
+ ti_flags = current_thread_info()->flags;
if (unlikely(r3 >= (unsigned long)-MAX_ERRNO) && is_not_scv) {
if (likely(!(ti_flags & (_TIF_NOERROR | _TIF_RESTOREALL)))) {
@@ -271,7 +270,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
ret = _TIF_RESTOREALL;
else
regs->gpr[3] = r3;
- clear_bits(_TIF_PERSYSCALL_MASK, ti_flagsp);
+ clear_bits(_TIF_PERSYSCALL_MASK, ¤t_thread_info()->flags);
} else {
regs->gpr[3] = r3;
}
@@ -284,7 +283,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
local_irq_disable();
again:
- ti_flags = READ_ONCE(*ti_flagsp);
+ ti_flags = READ_ONCE(current_thread_info()->flags);
while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) {
local_irq_enable();
if (ti_flags & _TIF_NEED_RESCHED) {
@@ -300,7 +299,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
do_notify_resume(regs, ti_flags);
}
local_irq_disable();
- ti_flags = READ_ONCE(*ti_flagsp);
+ ti_flags = READ_ONCE(current_thread_info()->flags);
}
if (IS_ENABLED(CONFIG_PPC_BOOK3S) && IS_ENABLED(CONFIG_PPC_FPU)) {
@@ -357,7 +356,6 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
#ifndef CONFIG_PPC_BOOK3E_64 /* BOOK3E not yet using this */
notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned long msr)
{
- unsigned long *ti_flagsp = ¤t_thread_info()->flags;
unsigned long ti_flags;
unsigned long flags;
unsigned long ret = 0;
@@ -380,7 +378,7 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned
local_irq_save(flags);
again:
- ti_flags = READ_ONCE(*ti_flagsp);
+ ti_flags = READ_ONCE(current_thread_info()->flags);
while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) {
local_irq_enable(); /* returning to user: may enable */
if (ti_flags & _TIF_NEED_RESCHED) {
@@ -391,7 +389,7 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned
do_notify_resume(regs, ti_flags);
}
local_irq_disable();
- ti_flags = READ_ONCE(*ti_flagsp);
+ ti_flags = READ_ONCE(current_thread_info()->flags);
}
if (IS_ENABLED(CONFIG_PPC_BOOK3S) && IS_ENABLED(CONFIG_PPC_FPU)) {
@@ -443,7 +441,6 @@ void preempt_schedule_irq(void);
notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsigned long msr)
{
- unsigned long *ti_flagsp = ¤t_thread_info()->flags;
unsigned long flags;
unsigned long ret = 0;
#ifdef CONFIG_PPC64
@@ -466,8 +463,8 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsign
amr = kuap_get_and_check_amr();
#endif
- if (unlikely(*ti_flagsp & _TIF_EMULATE_STACK_STORE)) {
- clear_bits(_TIF_EMULATE_STACK_STORE, ti_flagsp);
+ if (unlikely(current_thread_info()->flags & _TIF_EMULATE_STACK_STORE)) {
+ clear_bits(_TIF_EMULATE_STACK_STORE, ¤t_thread_info()->flags);
ret = 1;
}
@@ -479,7 +476,7 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsign
again:
if (IS_ENABLED(CONFIG_PREEMPT)) {
/* Return to preemptible kernel context */
- if (unlikely(*ti_flagsp & _TIF_NEED_RESCHED)) {
+ if (unlikely(current_thread_info()->flags & _TIF_NEED_RESCHED)) {
if (preempt_count() == 0)
preempt_schedule_irq();
}
--
2.25.0
next prev parent reply other threads:[~2021-02-10 8:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-09 19:29 [PATCH v6 0/2] powerpc/32: Implement C syscall entry/exit (complement) Christophe Leroy
2021-02-09 19:29 ` [PATCH v6 1/2] powerpc/syscall: Do not check unsupported scv vector on PPC32 Christophe Leroy
2021-02-09 19:29 ` [PATCH v6 2/2] powerpc/32: Handle bookE debugging in C in syscall entry/exit Christophe Leroy
2021-02-10 8:44 ` Christophe Leroy [this message]
2021-02-12 0:19 ` [PATCH v6 0/2] powerpc/32: Implement C syscall entry/exit (complement) Michael Ellerman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ad0363ff0ff8c125f40e1cdc589a85bbd7e31693.1612946484.git.christophe.leroy@csgroup.eu \
--to=christophe.leroy@csgroup.eu \
--cc=benh@kernel.crashing.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mpe@ellerman.id.au \
--cc=msuchanek@suse.de \
--cc=npiggin@gmail.com \
--cc=paulus@samba.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).