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| author |   Valentin Schneider <vschneid@redhat.com> | 2022-06-30 23:32:57 +0100 |
|---|---|---|
| committer |   Andrew Morton <akpm@linux-foundation.org> | 2022-09-11 21:55:06 -0700 |
| commit | 7bb5da0d490b2d836c5218f5186ee588d2145310 (patch) | |
| tree | 2b6b1003e79581a22fa0438c40d48e42a645806a /kernel/kexec_core.c | |
| parent | lib/cmdline: avoid page fault in next_arg (diff) | |
| download | linux-dev-7bb5da0d490b2d836c5218f5186ee588d2145310.tar.xz linux-dev-7bb5da0d490b2d836c5218f5186ee588d2145310.zip | |
kexec: turn all kexec_mutex acquisitions into trylocks
Patch series "kexec, panic: Making crash_kexec() NMI safe", v4.
This patch (of 2):
Most acquistions of kexec_mutex are done via mutex_trylock() - those were
a direct "translation" from:
8c5a1cf0ad3a ("kexec: use a mutex for locking rather than xchg()")
there have however been two additions since then that use mutex_lock():
crash_get_memory_size() and crash_shrink_memory().
A later commit will replace said mutex with an atomic variable, and
locking operations will become atomic_cmpxchg(). Rather than having those
mutex_lock() become while (atomic_cmpxchg(&lock, 0, 1)), turn them into
trylocks that can return -EBUSY on acquisition failure.
This does halve the printable size of the crash kernel, but that's still
neighbouring 2G for 32bit kernels which should be ample enough.
Link: https://lkml.kernel.org/r/20220630223258.4144112-1-vschneid@redhat.com
Link: https://lkml.kernel.org/r/20220630223258.4144112-2-vschneid@redhat.com
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: Juri Lelli <jlelli@redhat.com>
Cc: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'kernel/kexec_core.c')
| -rw-r--r-- | kernel/kexec_core.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index acd029b307e4..8fa4eeb95b30 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -1004,13 +1004,16 @@ void crash_kexec(struct pt_regs *regs) } } -size_t crash_get_memory_size(void) +ssize_t crash_get_memory_size(void) { - size_t size = 0; + ssize_t size = 0; + + if (!mutex_trylock(&kexec_mutex)) + return -EBUSY; - mutex_lock(&kexec_mutex); if (crashk_res.end != crashk_res.start) size = resource_size(&crashk_res); + mutex_unlock(&kexec_mutex); return size; } @@ -1022,7 +1025,8 @@ int crash_shrink_memory(unsigned long new_size) unsigned long old_size; struct resource *ram_res; - mutex_lock(&kexec_mutex); + if (!mutex_trylock(&kexec_mutex)) + return -EBUSY; if (kexec_crash_image) { ret = -ENOENT; |