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| author |   Thomas Gleixner <tglx@linutronix.de> | 2019-11-11 23:03:22 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2019-11-16 11:24:02 +0100 |
| commit | 060aa16fdb7c5078a4159a76e5dc87d6a493af9b (patch) | |
| tree | 63f2ffbc60ce9e1064ca13bc128efeb7c1e7f6c8 /arch/x86/kernel/ioport.c | |
| parent | x86/ioperm: Move iobitmap data into a struct (diff) | |
| download | linux-dev-060aa16fdb7c5078a4159a76e5dc87d6a493af9b.tar.xz linux-dev-060aa16fdb7c5078a4159a76e5dc87d6a493af9b.zip | |
x86/ioperm: Add bitmap sequence number
Add a globally unique sequence number which is incremented when ioperm() is
changing the I/O bitmap of a task. Store the new sequence number in the
io_bitmap structure and compare it with the sequence number of the I/O
bitmap which was last loaded on a CPU. Only update the bitmap if the
sequence is different.
That should further reduce the overhead of I/O bitmap scheduling when there
are only a few I/O bitmap users on the system.
The 64bit sequence counter is sufficient. A wraparound of the sequence
counter assuming an ioperm() call every nanosecond would require about 584
years of uptime.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/kernel/ioport.c')
| -rw-r--r-- | arch/x86/kernel/ioport.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c index 05f77f3af46d..7c1ab5c2b395 100644 --- a/arch/x86/kernel/ioport.c +++ b/arch/x86/kernel/ioport.c @@ -14,6 +14,8 @@ #include <asm/io_bitmap.h> #include <asm/desc.h> +static atomic64_t io_bitmap_sequence; + /* * this changes the io permissions bitmap in the current task. */ @@ -72,6 +74,9 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on) /* Update the thread data */ iobm->max = bytes; + /* Update the sequence number to force an update in switch_to() */ + iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence); + /* * Store the bitmap pointer (might be the same if the task already * head one). Set the TIF flag, just in case this is the first |