ps3fb: fix deadlock on kexec()
Since the introduction of the acquire_console_sem calls in
0333d83509
, kexecing can cause the
kernel to deadlock:
ps3fb_shutdown()
-> unregister_framebuffer()
-> fb_notifier_call_chain(FB_EVENT_FB_UNBIND)
-> fbcon_fb_unbind()
-> unbind_con_driver()
-> bind_con_driver()
[ acquires console_sem ]
-> fbcon_deinit()
-> fbops->fb_release(newinfo, 0)
-> ps3fb_release()
-> ps3fb_sync()
[ acquires console_sem ]
This change avoids the deadlock by moving the acquire_console_sem()
out of ps3fb_sync(), and puts it into the two other callsites, leaving
ps3fb_release() to call ps3fb_sync() without the console semaphore.
[Geert]
- Corrected call sequence above
- ps3fb_release() may be called with and without console_sem held. This is an
inconsistency that should be fixed at the fb level, but for now, try to
acquire console_sem in ps3fb_release().
I think it's safer to let ps3fb_release() try to acquire console_sem and
not refresh the screen if it fails, than to call ps3fb_sync() without
holding console_sem, as ps3fb_par may be modified at the same time, causing
crashes or lockups.
Besides, ps3fb_release() only calls ps3fb_sync() to refresh the screen
when display flipping is disabled, which is an uncommon case (except during
shutdown/kexec).
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
ba21611c9c
commit
8dab637612
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@ -443,8 +443,6 @@ static int ps3fb_sync(struct fb_info *info, u32 frame)
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u32 ddr_line_length, xdr_line_length;
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u64 ddr_base, xdr_base;
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acquire_console_sem();
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if (frame > par->num_frames - 1) {
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dev_dbg(info->device, "%s: invalid frame number (%u)\n",
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__func__, frame);
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@ -464,7 +462,6 @@ static int ps3fb_sync(struct fb_info *info, u32 frame)
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xdr_line_length);
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out:
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release_console_sem();
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return error;
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}
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@ -479,7 +476,10 @@ static int ps3fb_release(struct fb_info *info, int user)
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if (atomic_dec_and_test(&ps3fb.f_count)) {
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if (atomic_read(&ps3fb.ext_flip)) {
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atomic_set(&ps3fb.ext_flip, 0);
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ps3fb_sync(info, 0); /* single buffer */
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if (!try_acquire_console_sem()) {
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ps3fb_sync(info, 0); /* single buffer */
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release_console_sem();
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}
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}
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}
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return 0;
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@ -865,7 +865,9 @@ static int ps3fb_ioctl(struct fb_info *info, unsigned int cmd,
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break;
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dev_dbg(info->device, "PS3FB_IOCTL_FSEL:%d\n", val);
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acquire_console_sem();
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retval = ps3fb_sync(info, val);
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release_console_sem();
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break;
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default:
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@ -885,7 +887,9 @@ static int ps3fbd(void *arg)
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set_current_state(TASK_INTERRUPTIBLE);
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if (ps3fb.is_kicked) {
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ps3fb.is_kicked = 0;
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acquire_console_sem();
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ps3fb_sync(info, 0); /* single buffer */
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release_console_sem();
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}
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schedule();
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}
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