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Wed, 4 Mar 2020 18:30:24 +0000 From: Song Liu To: Yonghong Song CC: Andrii Nakryiko , bpf , Alexei Starovoitov , Daniel Borkmann , Kernel Team Subject: Re: [PATCH bpf v2 2/2] selftests/bpf: add send_signal_sched_switch test Thread-Topic: [PATCH bpf v2 2/2] selftests/bpf: add send_signal_sched_switch test Thread-Index: AQHV8k3x064hLfnWp0aT76+XdkBMDqg4u0sAgAAA7gCAAAUbAA== Date: Wed, 4 Mar 2020 18:30:24 +0000 Message-ID: References: <20200304175310.2389842-1-yhs@fb.com> <20200304175311.2389987-1-yhs@fb.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3608.60.0.2.5) x-originating-ip: [2620:10d:c090:400::5:4f8d] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: c2dfa745-e44b-4148-bfd6-08d7c06a1aff x-ms-traffictypediagnostic: MW3PR15MB3836: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-fb-source: Internal x-ms-oob-tlc-oobclassifiers: OLM:37; x-forefront-prvs: 0332AACBC3 x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(396003)(366004)(376002)(346002)(136003)(39860400002)(199004)(189003)(86362001)(6486002)(2906002)(6636002)(6512007)(4326008)(6862004)(8676002)(8936002)(186003)(81166006)(5660300002)(81156014)(6506007)(53546011)(64756008)(66946007)(478600001)(2616005)(66476007)(66556008)(36756003)(33656002)(316002)(54906003)(37006003)(71200400001)(76116006)(66446008);DIR:OUT;SFP:1102;SCL:1;SRVR:MW3PR15MB3836;H:MW3PR15MB3882.namprd15.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:1;MX:1; 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This test can be use= d >>> to verify kernel deadlocks fixed by the previous commit. The test itsel= f >>> is heavily borrowed from Commit eac9153f2b58 ("bpf/stackmap: Fix deadlo= ck >>> with rq_lock in bpf_get_stack()"). >>>=20 >>> Cc: Song Liu >>> Signed-off-by: Yonghong Song >>> --- >>> .../bpf/prog_tests/send_signal_sched_switch.c | 89 +++++++++++++++++++ >>> .../bpf/progs/test_send_signal_kern.c | 6 ++ >>> 2 files changed, 95 insertions(+) >>> create mode 100644 tools/testing/selftests/bpf/prog_tests/send_signal_= sched_switch.c >>>=20 >>> diff --git a/tools/testing/selftests/bpf/prog_tests/send_signal_sched_s= witch.c b/tools/testing/selftests/bpf/prog_tests/send_signal_sched_switch.c >>> new file mode 100644 >>> index 000000000000..f5c9dbdeb173 >>> --- /dev/null >>> +++ b/tools/testing/selftests/bpf/prog_tests/send_signal_sched_switch.c >>> @@ -0,0 +1,89 @@ >>> +// SPDX-License-Identifier: GPL-2.0 >>> +#include >>> +#include >>> +#include >>> +#include >>> +#include >>> +#include >>> +#include >>> +#include >>> +#include "test_send_signal_kern.skel.h" >>> + >>> +static void sigusr1_handler(int signum) >>> +{ >>> +} >>> + >>> +#define THREAD_COUNT 100 >>> + >>> +static char *filename; >>> + >>> +static void *worker(void *p) >>> +{ >>> + int err, fd, i =3D 0; >>> + u32 duration =3D 0; >>> + char *pptr; >>> + void *ptr; >>> + >>> + fd =3D open(filename, O_RDONLY); >>> + if (CHECK(fd < 0, "open", "open failed %s\n", strerror(errno))) >>> + return NULL; >>> + >>> + while (i < 100) { >>> + struct timespec ts =3D {0, 1000 + rand() % 2000}; >>> + >>> + ptr =3D mmap(NULL, 4096 * 64, PROT_READ, MAP_PRIVATE, f= d, 0); >>> + err =3D errno; >>> + usleep(1); >>> + if (CHECK(ptr =3D=3D MAP_FAILED, "mmap", "mmap failed: = %s\n", >>> + strerror(err))) >>> + break; >>> + >>> + munmap(ptr, 4096 * 64); >>> + usleep(1); >>> + pptr =3D malloc(1); >>> + usleep(1); >>> + pptr[0] =3D 1; >>> + usleep(1); >>> + free(pptr); >>> + usleep(1); >>> + nanosleep(&ts, NULL); >>> + i++; >> Any specific reason to do mmap()/munmap() in a loop? Would, say, >> getpid syscall work just fine as well to trigger a bunch of context >> switches? Or event just usleep(1) alone? >=20 > No particular reason. Copied from Song's original reproducer and > it is working. Maybe Song can comment why it is written this way. In that test, mmap/munmap are used to lock mmap_sem. I guess we=20 don't really need them in this test.=20 Thanks, song=