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  1. 27 Oct, 2023 1 commit
  3. 17 Oct, 2023 1 commit
  5. 16 Oct, 2023 1 commit
  7. 14 Oct, 2023 1 commit
    • Ingo Molnar's avatar
      locking/seqlock: Propagate 'const' pointers within read-only methods, remove forced type casts · 886ee55e
      Ingo Molnar authored 
      Currently __seqprop_ptr() is an inline function that must chose to either
use 'const' or non-const seqcount related pointers - but this results in
the undesirable loss of 'const' propagation, via a forced type cast.

The easiest solution would be to turn the pointer wrappers into macros that
pass through whatever type is passed to them - but the clever maze of
seqlock API instantiation macros relies on the GCC CPP '##' macro
extension, which isn't recursive, so inline functions must be used here.

So create two wrapper variants instead: 'ptr' and 'const_ptr', and pick the
right one for the codepaths that are const: read_seqcount_begin() and
read_seqcount_retry().

This cleans up type handling and allows the removal of all type forcing.

No change in functionality.
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul E. McKenney <paulmck@kernel.org>
      886ee55e
  9. 12 Oct, 2023 3 commits
    • Lucy Mielke's avatar
      locking/lockdep: Fix string sizing bug that triggers a format-truncation compiler-warning · ac8b60be
      Lucy Mielke authored 
      On an allyesconfig, with "treat warnings as errors" unset, GCC emits
these warnings:

	kernel/locking/lockdep_proc.c:438:32: Warning: Format specifier '%lld' may
		be truncated when writing 1 to 17 bytes into a region
		of size 15 [-Wformat-truncation=]

	kernel/locking/lockdep_proc.c:438:31: Note: Format directive argument is
		in the range [-9223372036854775, 9223372036854775]

	kernel/locking/lockdep_proc.c:438:9: Note: 'snprintf' has output
		between 5 and 22 bytes into a target of size 15

In seq_time(), the longest s64 is "-9223372036854775808"-ish, which
converted to the fixed-point float format is "-9223372036854775.80": 21 bytes,
plus termination is another byte: 22. Therefore, a larger buffer size
of 22 is needed here - not 15. The code was safe due to the snprintf().

Fix it.
Signed-off-by: default avatarLucy Mielke <lucymielke@icloud.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/ZSfOEHRkZAWaQr3U@fedora.fritz.box
      ac8b60be
    • Oleg Nesterov's avatar
      locking/seqlock: Change __seqprop() to return the function pointer · e6115c6f
      Oleg Nesterov authored 
      This simplifies the macro and makes it easy to add the new seqprop's
with 2 or more args.

Plus this way we do not lose the type info, the (void*) type cast is
no longer needed.

And the latter reveals the problem: a lot of seqcount_t helpers pass
the "const seqcount_t *s" argument to __seqprop_ptr(seqcount_t *s)
but (before this patch) "(void *)(s)" masked the problem.

So this patch changes __seqprop_ptr() and __seqprop_##lockname##_ptr()
to accept the "const LOCKNAME *s" argument. This is not nice either,
they need to drop the constness on return because these helpers are used
by both the readers and writers, but at least it is clear what's going on.
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20231012143227.GA16143@redhat.com
      e6115c6f
    • Oleg Nesterov's avatar
      locking/seqlock: Simplify SEQCOUNT_LOCKNAME() · f995443f
      Oleg Nesterov authored 
      1. Kill the "lockmember" argument. It is always s->lock plus
   __seqprop_##lockname##_sequence() already uses s->lock and
   ignores "lockmember".

2. Kill the "lock_acquire" argument. __seqprop_##lockname##_sequence()
   can use the same "lockbase" prefix for _lock and _unlock.

Apart from line numbers, gcc -E outputs the same code.
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20231012143158.GA16133@redhat.com
      f995443f
  11. 10 Oct, 2023 1 commit
  13. 09 Oct, 2023 4 commits
    • Uros Bizjak's avatar
      locking/atomic, xen: Use sync_try_cmpxchg() instead of sync_cmpxchg() · ad0a2e4c
      Uros Bizjak authored 
      Use sync_try_cmpxchg() instead of sync_cmpxchg(*ptr, old, new) == old
in clear_masked_cond(), clear_linked() and
gnttab_end_foreign_access_ref_v1(). x86 CMPXCHG instruction returns
success in ZF flag, so this change saves a compare after cmpxchg
(and related move instruction in front of cmpxchg), improving the
cmpxchg loop in gnttab_end_foreign_access_ref_v1() from:

     174:	eb 0e                	jmp    184 <...>
     176:	89 d0                	mov    %edx,%eax
     178:	f0 66 0f b1 31       	lock cmpxchg %si,(%rcx)
     17d:	66 39 c2             	cmp    %ax,%dx
     180:	74 11                	je     193 <...>
     182:	89 c2                	mov    %eax,%edx
     184:	89 d6                	mov    %edx,%esi
     186:	66 83 e6 18          	and    $0x18,%si
     18a:	74 ea                	je     176 <...>

to:

     614:	89 c1                	mov    %eax,%ecx
     616:	66 83 e1 18          	and    $0x18,%cx
     61a:	75 11                	jne    62d <...>
     61c:	f0 66 0f b1 0a       	lock cmpxchg %cx,(%rdx)
     621:	75 f1                	jne    614 <...>

No functional change intended.
Signed-off-by: default avatarUros Bizjak <ubizjak@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarJuergen Gross <jgross@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
      ad0a2e4c
    • Uros Bizjak's avatar
      locking/atomic/x86: Introduce arch_sync_try_cmpxchg() · 636d6a8b
      Uros Bizjak authored 
      Introduce the arch_sync_try_cmpxchg() macro to improve code using
sync_try_cmpxchg() locking primitive. The new definitions use existing
__raw_try_cmpxchg() macros, but use its own "lock; " prefix.

The new macros improve assembly of the cmpxchg loop in
evtchn_fifo_unmask() from drivers/xen/events/events_fifo.c from:

 57a:	85 c0                	test   %eax,%eax
 57c:	78 52                	js     5d0 <...>
 57e:	89 c1                	mov    %eax,%ecx
 580:	25 ff ff ff af       	and    $0xafffffff,%eax
 585:	c7 04 24 00 00 00 00 	movl   $0x0,(%rsp)
 58c:	81 e1 ff ff ff ef    	and    $0xefffffff,%ecx
 592:	89 4c 24 04          	mov    %ecx,0x4(%rsp)
 596:	89 44 24 08          	mov    %eax,0x8(%rsp)
 59a:	8b 74 24 08          	mov    0x8(%rsp),%esi
 59e:	8b 44 24 04          	mov    0x4(%rsp),%eax
 5a2:	f0 0f b1 32          	lock cmpxchg %esi,(%rdx)
 5a6:	89 04 24             	mov    %eax,(%rsp)
 5a9:	8b 04 24             	mov    (%rsp),%eax
 5ac:	39 c1                	cmp    %eax,%ecx
 5ae:	74 07                	je     5b7 <...>
 5b0:	a9 00 00 00 40       	test   $0x40000000,%eax
 5b5:	75 c3                	jne    57a <...>
 <...>

to:

 578:	a9 00 00 00 40       	test   $0x40000000,%eax
 57d:	74 2b                	je     5aa <...>
 57f:	85 c0                	test   %eax,%eax
 581:	78 40                	js     5c3 <...>
 583:	89 c1                	mov    %eax,%ecx
 585:	25 ff ff ff af       	and    $0xafffffff,%eax
 58a:	81 e1 ff ff ff ef    	and    $0xefffffff,%ecx
 590:	89 4c 24 04          	mov    %ecx,0x4(%rsp)
 594:	89 44 24 08          	mov    %eax,0x8(%rsp)
 598:	8b 4c 24 08          	mov    0x8(%rsp),%ecx
 59c:	8b 44 24 04          	mov    0x4(%rsp),%eax
 5a0:	f0 0f b1 0a          	lock cmpxchg %ecx,(%rdx)
 5a4:	89 44 24 04          	mov    %eax,0x4(%rsp)
 5a8:	75 30                	jne    5da <...>
 <...>
 5da:	8b 44 24 04          	mov    0x4(%rsp),%eax
 5de:	eb 98                	jmp    578 <...>

The new code removes move instructions from 585: 5a6: and 5a9:
and the compare from 5ac:. Additionally, the compiler assumes that
cmpxchg success is more probable and optimizes code flow accordingly.
Signed-off-by: default avatarUros Bizjak <ubizjak@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
      636d6a8b
    • Uros Bizjak's avatar
      locking/atomic: Add generic support for sync_try_cmpxchg() and its fallback · e01cc1e8
      Uros Bizjak authored 
      Provide the generic sync_try_cmpxchg() function from the
raw_ prefixed version, also adding explicit instrumentation.

The patch amends existing scripts to generate sync_try_cmpxchg()
locking primitive and its raw_sync_try_cmpxchg() fallback, while
leaving existing macros from the try_cmpxchg() family unchanged.

The target can define its own arch_sync_try_cmpxchg() to override the
generic version of raw_sync_try_cmpxchg(). This allows the target
to generate more optimal assembly than the generic version.

Additionally, the patch renames two scripts to better reflect
whet they really do.
Signed-off-by: default avatarUros Bizjak <ubizjak@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
      e01cc1e8
    • Ingo Molnar's avatar
      Merge tag 'v6.6-rc5' into locking/core, to pick up fixes · fdb8b7a1
      Ingo Molnar authored 
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      fdb8b7a1
  15. 08 Oct, 2023 4 commits
  17. 07 Oct, 2023 10 commits
  19. 06 Oct, 2023 14 commits
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