diff options
author | Vincenzo Frascino <vincenzo.frascino@arm.com> | 2019-06-21 11:52:29 +0200 |
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committer | Thomas Gleixner <tglx@linutronix.de> | 2019-06-22 21:21:05 +0200 |
commit | 00b26474c2f1613d7ab894c525f775c67c8a9e8f (patch) | |
tree | ec821728fc16277806e520618650cbbdb5159575 /include/vdso | |
parent | vdso: Define standardized vdso_datapage (diff) | |
download | linux-00b26474c2f1613d7ab894c525f775c67c8a9e8f.tar.xz linux-00b26474c2f1613d7ab894c525f775c67c8a9e8f.zip |
lib/vdso: Provide generic VDSO implementation
In the last few years the kernel gained quite some architecture specific
vdso implementations which contain very similar code.
Introduce a generic VDSO implementation of gettimeofday() which will be
shareable between architectures once they are converted over.
The implementation is based on the current x86 VDSO code.
[ tglx: Massaged changelog and made the kernel doc tabular ]
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Shijith Thotton <sthotton@marvell.com>
Tested-by: Andre Przywara <andre.przywara@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mips@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Mark Salyzyn <salyzyn@android.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Huw Davies <huw@codeweavers.com>
Link: https://lkml.kernel.org/r/20190621095252.32307-3-vincenzo.frascino@arm.com
Diffstat (limited to 'include/vdso')
-rw-r--r-- | include/vdso/helpers.h | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/include/vdso/helpers.h b/include/vdso/helpers.h new file mode 100644 index 000000000000..01641dbb68ef --- /dev/null +++ b/include/vdso/helpers.h @@ -0,0 +1,56 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __VDSO_HELPERS_H +#define __VDSO_HELPERS_H + +#ifndef __ASSEMBLY__ + +#include <vdso/datapage.h> + +static __always_inline u32 vdso_read_begin(const struct vdso_data *vd) +{ + u32 seq; + + while ((seq = READ_ONCE(vd->seq)) & 1) + cpu_relax(); + + smp_rmb(); + return seq; +} + +static __always_inline u32 vdso_read_retry(const struct vdso_data *vd, + u32 start) +{ + u32 seq; + + smp_rmb(); + seq = READ_ONCE(vd->seq); + return seq != start; +} + +static __always_inline void vdso_write_begin(struct vdso_data *vd) +{ + /* + * WRITE_ONCE it is required otherwise the compiler can validly tear + * updates to vd[x].seq and it is possible that the value seen by the + * reader it is inconsistent. + */ + WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[CS_HRES_COARSE].seq + 1); + WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW].seq + 1); + smp_wmb(); +} + +static __always_inline void vdso_write_end(struct vdso_data *vd) +{ + smp_wmb(); + /* + * WRITE_ONCE it is required otherwise the compiler can validly tear + * updates to vd[x].seq and it is possible that the value seen by the + * reader it is inconsistent. + */ + WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[CS_HRES_COARSE].seq + 1); + WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW].seq + 1); +} + +#endif /* !__ASSEMBLY__ */ + +#endif /* __VDSO_HELPERS_H */ |