Date: Thu, 17 Mar 2022 10:00:20 GMT From: Hans Petter Selasky <hselasky@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: d17c5a4f6215 - stable/13 - LinuxKPI: Add comment describing proper use of the on_each_cpu() function. Message-ID: <202203171000.22HA0KWE089787@gitrepo.freebsd.org>
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The branch stable/13 has been updated by hselasky: URL: https://cgit.FreeBSD.org/src/commit/?id=d17c5a4f62157c665ecc187e676d52c07e841923 commit d17c5a4f62157c665ecc187e676d52c07e841923 Author: Hans Petter Selasky <hselasky@FreeBSD.org> AuthorDate: 2022-03-16 14:40:09 +0000 Commit: Hans Petter Selasky <hselasky@FreeBSD.org> CommitDate: 2022-03-17 09:55:15 +0000 LinuxKPI: Add comment describing proper use of the on_each_cpu() function. Sponsored by: NVIDIA Networking (cherry picked from commit c6cf874c7de3bcc092a58a932c732221b2933043) --- sys/compat/linuxkpi/common/include/linux/smp.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/sys/compat/linuxkpi/common/include/linux/smp.h b/sys/compat/linuxkpi/common/include/linux/smp.h index 290b91469b12..c6d011fceb5f 100644 --- a/sys/compat/linuxkpi/common/include/linux/smp.h +++ b/sys/compat/linuxkpi/common/include/linux/smp.h @@ -29,6 +29,18 @@ #ifndef _LINUXKPI_LINUX_SMP_H_ #define _LINUXKPI_LINUX_SMP_H_ +/* + * Important note about the use of the function provided below: + * + * The callback function passed to on_each_cpu() is called from a + * so-called critical section, and if you need a mutex you will have + * to rewrite the code to use native FreeBSD mtx spinlocks instead of + * the spinlocks provided by the LinuxKPI! Be very careful to not call + * any LinuxKPI functions inside the on_each_cpu()'s callback + * function, because they may sleep, unlike in native Linux. + * + * Enabling witness(4) when testing, can catch such issues. + */ #define on_each_cpu(cb, data, wait) ({ \ CTASSERT(wait); \ linux_on_each_cpu(cb, data); \
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